JP5250879B2 - Kerr effect microscope, magnetization direction measuring method, and Kerr effect microscope calibration method - Google Patents

Description

  The present invention relates to a Kerr effect microscope, a magnetization direction measuring method, and a Kerr effect microscope calibration method.

  The Kerr effect microscope uses the phenomenon (Kerr effect) that the polarization plane of reflected light rotates according to the magnitude of magnetization of the magnetic material when the magnetic material reflects linearly polarized light. Is a device that obtains magnetic characteristics of a magnetic material (see Patent Document 1). A Kerr effect microscope typically includes a light source, a polarizer, an objective lens facing a sample, an analyzer, and a detection device. As the detection device, an imaging device such as a CCD camera or a photoelectric conversion element such as a photodiode is used.

  The operation principle of the Kerr effect microscope is roughly as follows. By making the light generated by the light source enter the polarizer, probe light having linearly polarized light is generated, and the probe light is incident on the sample via the objective lens. The probe light is reflected by the sample, thereby generating reflected light. The polarization plane of the reflected light is rotated from the polarization plane of the probe light by the Kerr effect. The rotation angle of the polarization plane, that is, the Kerr rotation angle, depends on the magnitude of the probe light direction component of the magnetization of the sample and the magneto-optic coefficient of the sample. The reflected light reflected by the sample is incident on the analyzer via the objective lens, and the light that has passed through the analyzer is incident on the detection device. Since the intensity distribution of the light passing through the analyzer corresponds to the distribution of the magnitude of the probe light direction component of the magnetization of the sample, an image of the magnetic domain structure is obtained from the light passing through the analyzer, A distribution of the magnitude of magnetization can be obtained.

One problem with conventional Kerr effect microscopes is that only the magnitude of one unidirectional component of magnetization can be detected, that is, the direction of magnetization cannot be specified. The direction of magnetization is important information for knowing the characteristics of the magnetic material. Therefore, in the evaluation of the magnetic material, it is desirable that the direction of magnetization at each position of the sample can be specified. However, as far as the inventors know, there is no Kerr effect microscope having a function of specifying the direction of magnetization.
JP 2006-113527 A

  Accordingly, an object of the present invention is to provide a technique for specifying the direction of magnetization by the Kerr effect microscope.

  In order to achieve the above object, the present invention employs the means described below. In the description of the means, in order to clarify the correspondence between the description of [Claims] and the description of [Best Mode for Carrying Out the Invention], [Best Mode for Carrying Out the Invention] ] Are used for reference. However, the appended numbers and symbols should not be used to limit the technical scope of the invention described in [Claims].

  The Kerr effect microscope of the present invention is configured such that the first probe light (6x) is incident on the sample in the first direction and the second probe light (6y) is incident on the second direction different from the first direction. The light incident means (1, 2), the first reflected light (7x) generated by reflecting the first probe light (6x) by the sample, and the second probe light (6y) reflected by the sample. Magnetization direction specifying means (3, 4) for specifying the magnetization direction at each position of the sample from the generated second reflected light (7y). The first reflected light (7x) and the second reflected light (7y) contain information on the components in different directions of magnetization at each position of the sample. Therefore, in such a Kerr effect microscope, the sample It is possible to specify the magnetization direction at each of the positions.

  Preferably, the first direction is defined obliquely with respect to a vertical direction perpendicular to the surface of the sample in a plane of a first plane perpendicular to the surface of the sample, and the second direction is the first direction. It is defined obliquely with respect to the vertical direction in the plane of the second plane perpendicular to the first plane. The magnetization direction specifying means (3, 4) specifies, from the first reflected light (7x), a direction cosine of the magnetization of the sample in a direction in both the first plane and the surface of the sample. Then, the direction cosine of the magnetization of the sample in a direction in both the second plane and the surface of the sample is specified from the second reflected light (7y). In this specification, “specifying” a “direction cosine” not only calculates the value of the direction cosine itself, but also calculates a value corresponding to the direction cosine (for example, a value proportional to the direction cosine). Note that it is used in the meaning of including.

  The probe light incident means (1, 2) is preferably configured to make the first probe light (6x) and the second probe light (6y) incident on the sample in a time-sharing manner.

  As the probe light incident means for entering the probe light in different directions, the first semiconductor laser (11x) that generates the first laser light (18x) used for generating the first probe light (6x) is used. And a second semiconductor laser (11y) that generates a second laser beam (18y) that is used to generate the second probe beam (6y). In this case, the probe light incident means (1, 2) further passes the first shutter (19x) that passes or blocks the first laser light (18x) and the second laser light (18y). Or a second shutter (19y) for blocking. In this case, the first shutter (19x) and the second shutter (19y) are configured such that the first probe light (6x) and the second probe light (6y) are incident on the sample in a time-sharing manner. It is preferable that the first laser beam (18x) and the second laser beam (19x) respectively pass or be blocked.

  Each of the first probe light (6x) and the second probe light (6y) is preferably double-modulated.

  In order to specify the three-dimensional direction of magnetization at each position of the sample, the probe light incident means (1, 2) transmits the third probe light (6z) to the first direction and the second direction. It is preferable to be configured to be incident in different third directions. In this case, the magnetization direction specifying means (3, 4) determines the magnetization direction of the sample from the third reflected light (7z) generated by the third probe light (6z) being reflected by the sample. Identify.

  In this case, the third direction is defined as a vertical direction perpendicular to the surface of the sample, and the magnetization direction specifying means (3, 4) generates the magnetization of the sample from the first reflected light (7x). The direction cosine for the in-plane direction of both the first plane and the surface of the sample is specified, and the component in the in-plane direction of the second plane of the magnetization of the sample is determined from the second reflected light (7y). It is preferable to specify the vertical component of the magnetization of the sample from the third reflected light (7z).

  When the Kerr effect microscope of the present invention further includes a display device (5), the magnetization direction specifying means (3, 4) displays the display image indicating the direction of magnetization at each position of the sample. It is preferable to display on the device (5).

  In this case, the Kerr effect microscope further includes an external magnetic field applying device that applies a variable external magnetic field to the sample, and the magnetization direction specifying means (3, 4) is configured to transmit the external magnetic field by the external magnetic field applying device. It is preferable that the magnetization direction at each position of the sample is sequentially identified while the magnetization direction is changed, and the identified magnetization direction is displayed on the display device (5) as a moving image.

  The Kerr effect microscope further includes an external magnetic field application device that applies a variable external magnetic field to the sample, and a correspondence relationship between the Kerr rotation angle or ellipticity of the first reflected light (7x) and the external magnetic field. It is preferable to provide magnetization curve measuring means (3, 4) for obtaining a magnetization curve in a direction in both the first plane and the surface of the sample.

  In another embodiment, the probe light incident means (1, 2) has a single light source (11) and the first probe light (6x) by switching the optical path of the light generated by the light source (11). And a deflection mechanism (47) for generating the second probe light (6y).

  In one embodiment, the magnetization direction specifying means (3, 4) includes an imaging device (33) that acquires captured images of the first reflected light (7x) and the second reflected light (7y), and the captured image. To an arithmetic unit (4) for specifying the direction of magnetization at each position of the sample. In this case, the arithmetic unit (4) stores in advance correspondence data indicating a correspondence relationship between the luminance of each pixel in the captured image and the magnetization direction at each position of the sample, and It is preferable to specify the direction of magnetization at each position of the sample from the luminance and the corresponding data.

  In addition, the arithmetic device (4) previously stores correspondence data indicating a correspondence relationship between the luminance of each pixel in the captured image and the Kerr rotation angles of the first reflected light (7x) and the second reflected light (7y). The Kerr rotation angles of the first reflected light (7x) and the second reflected light (7y) are identified from the brightness of each pixel in the captured image and the corresponding data, and the identified Kerr rotation It is also preferable to specify the direction of magnetization at each position of the sample from the corner.

  The Kerr effect microscope further includes an external magnetic field application device that applies an external magnetic field to the sample, and the probe light incident means (1, 2) includes a first probe light (6x) and a second probe light (6y). ) Is incident on the sample, and the objective lens (23) which enters the first reflected light and the second reflected light (7y) reflected by the sample into the magnetization direction specifying means is provided. The effect microscope preferably includes a Faraday effect correction device (54, 56) for canceling a Faraday effect caused by a leakage magnetic field applied to the objective lens by the external magnetic field application device.

In one embodiment, the objective lens (23) directly faces the sample, and the first probe light (6x), the second probe light (6y), the first reflected light (7x), and the first The first lens (L ₁ ) through which the two reflected light (7y) passes, the first probe light (6x), the second probe light (6y), the first reflected light (7x), and the second reflected light. and a second lens (7y) passes _{(L 2),} the Faraday effect correction apparatus (54, 56) is a correction electromagnet (54) for applying a correcting magnetic field to the second lens _{(L 2)} It is preferable to include.

  In a preferred embodiment, the Faraday effect correction device (54, 56) further includes drive current supply means (56) for supplying a drive current to the correction electromagnet, and the drive current supply means (56) includes: The drive current is supplied to the correction electromagnet (54) in accordance with the external magnetic field generated by the external magnetic field application device.

  ADVANTAGE OF THE INVENTION According to this invention, the Kerr effect microscope which can pinpoint the direction of magnetization can be provided.

(Configuration of Kerr effect microscope)
FIG. 1 is a diagram showing a configuration of an optical system of a Kerr effect microscope according to an embodiment of the present invention. The Kerr effect microscope of FIG. 1 has a configuration for specifying the three-dimensional direction of magnetization of the sample S, that is, for specifying the direction cosine for each of the x, y, and z directions of magnetization. . In this specification, “specifying” a “direction cosine” not only calculates the value of the direction cosine itself, but also calculates a value corresponding to the direction cosine (for example, a value proportional to the direction cosine). Note that in the description of this embodiment, the x axis is defined in a specific direction in the plane of the surface of the sample S, and the y axis is in the plane of the surface of the sample S. Note that and is defined in a direction perpendicular to the x-axis, and the z-axis is defined in a direction perpendicular to both the x-axis and the y-axis, ie, a direction perpendicular to the surface of the sample S. .

  More specifically, the Kerr effect microscope shown in FIG. 1 is roughly composed of an incident optical system 1, an epi-illumination optical system 2, a detection optical system 3, an arithmetic device 4, and a display device 5. Yes.

  The incident optical system 1 has a function of generating probe lights 6x, 6y, and 6z. Here, the probe lights 6x, 6y, and 6z are probe lights used for specifying direction cosines for the x direction, the y direction, and the z direction of the magnetization of the sample S, respectively. Specifically, the incident optical system 1 includes three laser diodes 11x, 11y, and 11z, lenses 12x, 12y, and 12z, mirrors 13 and 14, half mirrors 15 and 16, and a polarizer 17. . The laser diodes 11x, 11y, and 11z are used as light sources that generate laser beams 18x, 18y, and 18z, respectively. The laser light 18x generated by the laser diode 11x is incident on the lens 12x, and the laser light 18x that has passed through the lens 12x is reflected by the mirror 13 and the half mirror 16 and is incident on the polarizer 17. Linearly polarized light having a polarization plane in a desired direction is extracted from the laser light 18x by the polarizer 17, and is emitted as probe light 6x. On the other hand, the light 18 y generated by the laser diode 11 y is incident on the lens 12 y, and the laser light 18 y that has passed through the lens 12 y is reflected by the mirror 13 and the half mirror 15 and is incident on the polarizer 17. The linearly polarized light having a desired plane of polarization is extracted from the light 18y by the polarizer 17 and emitted as probe light 6y. Similarly, the light 18z generated by the laser diode 11z is incident on the lens 12z, and the laser light 18z that has passed through the lens 12x is further incident on the polarizer 17 through the half mirrors 15 and 16. A desired linearly polarized light component is extracted from the light 18z by the polarizer 17 and emitted as probe light 6z. The optical axes of the probe lights 6x, 6y, and 6z are parallel to each other, but their positions do not match.

  The epi-illumination optical system 2 has a function of causing the probe lights 6x, 6y, and 6z to enter the sample S in a desired direction, and further causing the reflected lights 7x, 7y, and 7z from the sample S to enter the detection optical system 3. Yes. In the present embodiment, the Smith mirror method is employed for the incident light optical system 2. This is because the Smith mirror method has a suitable configuration for directing the probe lights 6x, 6y, and 6z having different optical axis positions to the sample S. More specifically, the incident optical system 2 includes a Smith mirror 21, a half mirror 22, and an objective lens 23. The probe lights 6x, 6y, and 6z incident from the incident optical system 1 are reflected by the Smith mirror 21 and the half mirror 22 and are incident on the objective lens 23. The objective lens 23 makes the probe lights 6x, 6y, and 6z enter the sample S, and the reflected lights 7x, 7y, and 7z from the sample S enter the detection optical system 3 through the half mirror 22.

  The detection optical system 3 includes an analyzer 31, an imaging lens 32, and a CCD camera 33. The reflected lights 7x, 7y and 7z are incident on the CCD camera 33 via the analyzer 31 and the imaging lens 32. The CCD camera 33 captures captured images of the incident reflected light 7x, 7y, and 7z and sends the captured images to the arithmetic unit 4. The luminance of each pixel of the captured image indicates the light intensity at each position of the spot of the reflected light 7x, 7y, 7z. The CCD camera 33 includes a shutter (not shown), and is configured to be able to capture captured images of reflected light 7x, 7y, and 7z only at a desired time.

  The arithmetic device 4 processes captured images of the reflected lights 7x, 7y, and 7z captured by the CCD camera 33. Specifically, the arithmetic device 4 specifies direction cosines for the x direction, the y direction, and the z direction of the magnetization at each position of the sample S from the captured images of the reflected lights 7x, 7y, and 7z, respectively. In addition, the arithmetic device 4 processes captured images of the reflected lights 7x, 7y, and 7z to generate a display image to be displayed on the display device 5. The display device 5 displays the display image sent from the arithmetic device 4.

  In order to make it possible to specify the x component, the y component, and the z component of the magnetization of the sample S, the incident optical system 1 and the incident optical system 2 of the Kerr effect microscope of the present embodiment apply the probe lights 6x, 6y, and 6z to the sample S. Are made to enter the sample S from the same position and from different directions. FIG. 2 is a diagram illustrating a direction in which the probe lights 6x, 6y, and 6z are incident and a direction in which the reflected lights 7x, 7y, and 7z are reflected.

  As shown in FIG. 2, the probe light 6x is incident in a direction parallel to the zx plane and oblique to the z axis. That is, the incident direction of the probe light 6x is adjusted so that the incident surface defined by the probe light 6x and the reflected light 7x is parallel to the zx plane. When the probe light 6x is incident in such a direction, reflection occurs due to the vertical Kerr effect due to the x component Hx of the magnetic field generated by the magnetization M of the sample S, as shown in FIG. The polarization plane of the light 7x rotates from the polarization plane of the probe light 6x. As will be described later, the direction cosine of the direction of the magnetization M of the sample S in the x direction is specified from the rotation angle of the polarization plane of the reflected light 7x (that is, the Kerr rotation angle of the reflected light 7x).

  In order to make the probe light 6x incident in a direction parallel to the zx plane, as shown in FIG. 4A, each of the incident optical system 1 and the incident optical system 2 includes the probe light 6x. The optical axis of the objective lens 23 is adjusted so as to be incident on a predetermined position defined on the x ′ axis of the body surface of the objective lens 23 (the contact surface at the base of the objective lens 23). Here, the x′-y ′ coordinate system is a coordinate system defined on the body-mounted surface of the objective lens 23 with the position of the optical axis of the objective lens 23 as the origin, and the x ′ axis is x in the real space. The y ′ axis is an axis corresponding to the y ′ axis in real space.

  Referring to FIG. 2 again, the probe light 6y is incident in a direction parallel to the yz plane and oblique to the z axis. When the probe light 6y is incident in such a direction, reflection occurs due to the vertical Kerr effect due to the y component Hy of the magnetic field generated by the magnetization M of the sample S, as shown in FIG. The polarization plane of the light 7y rotates from the polarization plane of the probe light 6x. As will be described later, the direction cosine of the magnetization M of the sample S in the y direction is specified from the Kerr rotation angle of the reflected light 7x. In order to make the probe light 6y incident in a direction parallel to the yz plane, as shown in FIG. 4B, each of the optical elements of the incident optical system 1 and the incident optical system 2 has the probe light 6y The optical axis of the objective lens 23 is adjusted so as to be incident on a predetermined position defined on the y ′ axis of the body-mounted surface of the objective lens 23.

  Referring to FIG. 2 again, the probe light 6z is incident in a direction parallel to the z axis. When the probe light 6z is incident in such a direction, reflection occurs due to the polar Kerr effect due to the z component Hz of the magnetic field generated by the magnetization M of the sample S, as shown in FIG. The polarization plane of the light 7z rotates from the polarization plane of the probe light 6z. Note that the rotation of the polarization plane of the reflected light 7z is caused by the polar Kerr effect, unlike the reflected lights 7x and 7y. As will be described later, the direction cosine of the magnetization M of the sample S in the z direction is specified from the Kerr rotation angle of the reflected light 7z. In order to make the probe light 6z incident in a direction parallel to the z-axis, the optical elements of the incident optical system 1 and the epi-illumination optical system 2 are optical axes of the objective lens 23 as shown in FIG. Is adjusted to coincide with the optical axis of the probe light 6z.

(Operation of Kerr effect microscope)
Next, the operation of the Kerr effect microscope of the embodiment of FIG. 1, in particular, a method for specifying direction cosines in the x direction, y direction, and z direction in the direction of the magnetization M of the sample S will be described.
When obtaining a direction cosine of the magnetization M at each position of the sample S in the x direction, a drive current is supplied to the laser diode 11 x and the probe light 6 x is incident on the sample S. As described above, the probe light 6x is incident in a direction parallel to the zx plane and oblique to the z axis. The reflected light 7x generated by reflecting the probe light 6x by the sample S enters the analyzer 31, and the CCD camera 33 captures an image of the reflected light 7x that has passed through the analyzer 31. The luminance of each pixel of the captured image of the reflected light 7x corresponds to the direction cosine of the magnetization M in the x direction at each position of the sample S. This is because the intensity of the reflected light 7x that has passed through the analyzer 31 is determined by the Kerr rotation angle of the reflected light 7x (or the ellipticity of the reflected light 7x), and the Kerr rotation angle of the reflected light 7x (or the ellipticity of the reflected light 7x). ) Is determined by the x component Hx of the magnetic field generated by the magnetization M of the sample S, and the x component Hx of the magnetic field is determined by the x component Mx of the magnetization M of the sample S, that is, the direction cosine in the x direction. It is. The captured image of the reflected light 7x is sent to the arithmetic device 4, and the arithmetic device 4 specifies the direction cosine of the magnetization M in the x direction at each position of the sample S from the luminance of each pixel of the captured image of the reflected light 7x.

  Similarly, when obtaining the direction cosine of the magnetization M at each position of the sample S in the y direction, a drive current is supplied to the laser diode 11 y and the probe light 6 y is incident on the sample S. As described above, the probe light 6y is incident in a direction parallel to the yz plane and oblique to the z axis. The captured image of the reflected light 7 y that has passed through the analyzer 31 is captured by the CCD camera 33, and the captured image of the reflected light 7 y is sent to the arithmetic device 4. The arithmetic device 4 determines the direction cosine of the magnetization M in the y direction at each position of the sample S from the luminance of each pixel of the captured image of the reflected light 7y.

  Similarly, when obtaining the direction cosine of the magnetization M at each position of the sample S in the z direction, a drive current is supplied to the laser diode 11 z and the probe light 6 z is incident on the sample S. The captured image of the reflected light 7z that has passed through the analyzer 31 is captured by the CCD camera 33, and the captured image of the reflected light 7z is sent to the arithmetic unit 4. The arithmetic device 4 determines the direction cosine of the magnetization M in the z direction at each position of the sample S from the luminance of each pixel of the captured image of the reflected light 7z. By the above method, the direction cosine of the magnetization M at each position of the sample S in the x direction, the y direction, and the z direction, that is, the direction of the magnetization M at each position of the sample S is specified.

  In specifying the direction cosine, the value of the direction cosine itself may be obtained, or a value corresponding to the direction cosine on a one-to-one basis (for example, a value proportional to the direction cosine) may be obtained. Since the value corresponding to the direction cosine on a one-to-one basis represents the direction of magnetization in the same way as the direction cosine, it is technically equivalent to use the value corresponding to the direction cosine on a one-to-one basis instead of the value of the direction cosine itself. is there.

  The probe lights 6x, 6y, and 6z are preferably irradiated in a time division manner (not simultaneously). If the probe lights 6x, 6y, and 6z are generated so as not to interfere with each other (for example, if the probe lights 6x, 6y, and 6z are generated so as to have different wavelengths), in principle, the probe lights 6x, 6y, Even if 6z is irradiated at the same time, it is possible to specify the direction cosines of the magnetization M in each position of the sample S in the x, y, and z directions. However, from the viewpoint of more accurately specifying the direction cosines in the x direction, the y direction, and the z direction, the probe lights 6x, 6y, and 6z are preferably irradiated separately. When the sample light S is simultaneously irradiated with probe lights 6x, 6y, and 6z having different wavelengths, the Kerr rotation angle due to the Kerr effect is dependent on the wavelength, and therefore the direction cosines in the x, y, and z directions. In order to specify accurately, it is necessary to perform correction according to the wavelength. This is not preferable from the viewpoint of more accurately specifying the direction cosine in the x direction, the y direction, and the z direction.

  The arithmetic device 4 generates a display image indicating the direction of the magnetization M at each position of the sample S and displays it on the display device 5. In one embodiment, the arithmetic device 4 displays on the display device 5 a display image that represents the direction of the magnetization M at each position of the sample S by color. Such a display image is most simply expressed by the gradations of the three primary colors (red, green, and blue) of each pixel of the display image, and the luminance of each pixel of the captured image of reflected light 7x, 7y, and 7z, respectively. Can be generated by matching. For example, the red gradation of each pixel of the display image is determined so as to match the luminance of each pixel of the captured image of the reflected light 7x, and the green gradation matches the luminance of each pixel of the captured image of the reflected light 7y. The blue gradation is determined so as to match the luminance of each pixel of the captured image of the reflected light 7z. In the display image generated in this way, the magnetization directions of the magnetic domains generated in the sample S are illustrated by colors, and therefore it is easy to intuitively grasp the direction of each magnetic domain.

  The direction of the magnetization M at each position of the sample S can be displayed as a small arrow. In this case, the arithmetic unit 4 displays a 3D image of the sample S, and further displays a small arrow indicating the direction of the magnetization M at the position in an overlapping manner at each position of the 3D image. Thereby, the direction of the magnetization M at each position of the sample S can be visually grasped. The direction of the magnetization M at each position of the sample S can also be shown using both the color and the arrow at each position.

  The z component Mz of the magnetization M of the sample S may not be measured if it is not necessary. That is, only the direction of the magnetization M in the plane of the surface of the sample S may be measured. When the measurement target is a thin film, the direction of the magnetization M of the sample S is often in the in-plane direction of the surface of the sample S (that is, the direction parallel to the xy plane). In such a case, it is not necessary to measure the z component Mz of the magnetization M. When the z component Mz of the magnetization M is not measured, optical elements (for example, the laser diode 11z and the lens 12z) for generating the probe light 6z may be removed from the Kerr effect microscope. FIG. 5 shows an example of a display image displayed on the display device 5 when only the cosines of the magnetization M of the sample S in the x direction and the y direction are specified. In the display image of FIG. 5, the direction of the magnetization M at each position of the sample S is illustrated by a color and an arrow (note that FIG. 5 is illustrated in gray scale due to the restrictions of the JPO system. Please note.)

  When an external magnetic field is applied to the sample S while changing its magnitude and / or direction, the change in the direction of the magnetization M at each position of the sample S due to the external magnetic field can be displayed as a moving image. FIG. 6A is a timing chart showing an example of operation timing of the Kerr effect microscope when the change in the direction of the magnetization M at each position of the sample S is displayed as a moving image. In the operation of FIG. 6A, the external magnetic field applied to the sample S is increased stepwise, and the captured images of the reflected lights 7x, 7y, and 7z are sequentially captured in synchronization with the increase of the external magnetic field.

In particular, applied external magnetic field H ₁ of a certain magnitude to the sample S, in this state, the laser diode 11x, 11y, to 11z, the drive current is supplied sequentially. Accordingly, the probe lights 6x, 6y, and 6x are sequentially incident on the sample S. The shutter of the CCD camera 33 is opened in synchronization with the supply of drive current to the laser diodes 11x, 11y, and 11z. Thus, the reflected light 7x, 7y, captured image 7z are sequentially captured, the external magnetic field H ₁ is in a state of being applied to the sample S, the direction of magnetization M of the position of the sample S is specified.

Subsequently, a large external magnetic field _{H 2} than the external magnetic field _{H 1} is applied to the sample S, in this state, the laser diode 11x, 11y, to 11z, the drive current is supplied sequentially. Furthermore, the shutter of the CCD camera 33 is opened in synchronization with the supply of the drive current to the laser diodes 11x, 11y, and 11z. Thus, the reflected light 7x, 7y, captured image 7z are sequentially captured, the external magnetic field H ₂ is in a state of being applied to the sample S, the direction of magnetization M of the position of the sample S is specified. Subsequently, the direction of the magnetization M at each position of the sample S is specified while changing the magnitude of the external magnetic field by the same procedure, and the change in the direction of the magnetization M at each position of the sample S is displayed as a moving image. The

  Similarly, when only the direction cosines of the magnetization M of the sample S in the x direction and the y direction are specified (that is, when only the direction of the magnetization M in the plane of the surface of the sample S is measured), the external magnetic field is similarly measured. It is possible to display a change in the direction of the magnetization M at each position of the sample S as a moving image. FIG. 6B is a timing chart showing the operation timing of the Kerr effect microscope when the direction of the magnetization M in the surface of the sample S is displayed as a moving image. The external magnetic field applied to the sample S is increased stepwise, and driving current is supplied to the laser diodes 11x and 11y in synchronization with the increase of the external magnetic field. In synchronization with the supply of drive current to the laser diodes 11x and 11y, the shutter of the CCD camera 33 is opened, and the captured images of the reflected lights 7x and 7y are sequentially captured. From the captured images of the reflected lights 7x and 7y, a display image indicating the direction of the magnetization M is sequentially generated and displayed on the display device 5.

  In the Kerr effect microscope of the present embodiment, a magnetization curve with respect to a desired direction of magnetization at a desired position of the sample S can be obtained by performing measurement while changing the magnitude of the external magnetic field. Since the Kerr rotation angles θk (or ellipticity η) of the reflected lights 7x, 7y, and 7z correspond to the x component, the y component, and the z component of the magnetization of the sample S, respectively, the reflected lights 7x, 7y The curve indicating the dependence of the Kerr rotation angle θk (or ellipticity η) of 7z on the external magnetic field is equivalent to the magnetization curve. Therefore, the magnetization curve can be obtained by measuring the change in the Kerr rotation angle θk (or ellipticity η) with respect to the magnitude of the external magnetic field. The calculation of the magnetization curve is performed by the arithmetic device 4.

7A and 7B are diagrams showing examples of the obtained magnetization curves. Specifically, FIG. 7A shows a magnetization curve in the x direction of the magnetization of the sample S, and FIG. 7B shows a magnetization curve in the x direction. 7A and 7B, the external magnetic field is applied in the x-axis direction, and the Kerr rotation angles θk of the reflected lights 7x and 7y are measured while changing the magnitude of the external magnetic field. 7A and 7B, the Kerr rotation angle θk is normalized by the Kerr rotation angle θk ^sat when the external magnetic field is sufficiently large. Obtaining a magnetization curve is useful in evaluating the characteristics of the sample S.

The application of the external magnetic field to the sample S can be realized by, for example, a magnetic field application device shown in FIG. The magnetic field application apparatus in FIG. 7 is generally composed of an x-axis electromagnet 51 and a y-axis electromagnet 52. The x-axis electromagnet 51 is supplied with current Ix, x axis electromagnet 51 generates an external magnetic field Hx ^E in the x-axis direction. A y-axis electromagnet 52 is provided so as to surround the x-axis electromagnet 51. A current Iy is supplied to the y-axis electromagnet 52, and the y-axis electromagnet 52 generates an external magnetic field Hy ^E in the y-axis direction. The sample S (not shown in FIG. 7) is placed between the x-axis electromagnets 51. According to the magnetic field application apparatus of FIG. 7, an external magnetic field in an arbitrary direction parallel to the xy plane can be applied to the sample S by controlling the currents Ix and Iy.

It is preferable that the probe lights 6x, 6y, and 6x used for measurement are doubly modulated. This reduces the coherence of each of the probe lights 6x, 6y, 6x, and improves the measurement accuracy in the direction of the magnetization M of the sample S. If the coherence of the probe lights 6x, 6y, 6x is excessively high, the light reflected undesirably by the optical element of the Kerr effect microscope interferes with the probe lights 6x, 6y, 6x and / or the reflected lights 7x, 7y, 7z. As a result, the accuracy of the direction of the magnetization M of the sample S decreases. In order to prevent a decrease in accuracy due to undesired interference, it is preferable that the probe lights 6x, 6y, and 6x are doubly modulated to reduce the coherence of the probe lights 6x, 6y, and 6x. FIG. 9 is a diagram illustrating waveforms of the intensity of the probe lights 6x, 6y, and 6x when the probe lights 6x, 6y, and 6x are doubly modulated. Double modulated probe light 6x, 6y, strength of 6x, the rectangular wave having a frequency f ₁ further has a modulated waveform with a frequency f _2. Here, the frequency _{f 2} is extremely higher than the frequency _{f 1.} Typically, the frequency f ₁ is a frequency on the order of 100 kHz, and the frequency f ₂ is a frequency on the order of several tens of MHz. The probe lights 6x, 6y and 6x having such an intensity waveform can be generated by flowing a drive current having a similar waveform.

(Modification)
6A and 6B, switching of the incident direction of the probe light (that is, switching of the probe lights 6x, 6y, and 6z) is performed by controlling the supply of drive current to the laser diodes 11x, 11y, and 11z. However, as shown in FIG. 10A, the incident direction of the probe light can be switched by the shutters 19x, 19y, and 19z. The shutters 19x, 19y, and 19z have a function of passing or blocking the laser beams 18x, 18y, and 18z, thereby controlling the irradiation of the probe beams 6x, 6y, and 6z. When the probe light 6x is incident on the sample S, the shutter 19x is opened and the shutters 19y and 19z are closed. Similarly, when the probe light 6y is incident on the sample S, the shutter 19y is opened and the shutters 19x and 19z are closed. Further, when the probe light 6z is incident on the sample S, the shutter 19z is opened and the shutters 19x and 19y are closed. As the shutters 19x, 19y, and 19z, not only a mechanical shutter but also a liquid crystal modulator, an EO modulator that uses an electro-optic effect (EO effect), and an AO modulator that uses an acousto-optic effect (AO effect) can be used. .

  As shown in FIG. 10B, instead of the three laser diodes 11x, 11y, and 11z, a deflection mechanism that switches the optical path of the probe light is provided, so that the incident direction of the probe light can be switched. Is possible. In detail, the incident optical system 1A of the Kerr effect microscope of FIG. 10 includes a light source 41, a condenser lens 42, an aperture stop 43, a field stop 44, a collimator lens 45, a mirror 46, a movable mirror 47, A relay lens 48 and a polarizer 49 are provided. The light generated by the light source 41 is incident on the mirror 46 via the condenser lens 42, the aperture stop 43, the field stop 44, and the collimator lens 45, and further reflected by the mirror 46 and incident on the movable mirror 47. . The movable mirror 47 is configured to be rotatable about the x axis and the z axis. The light reflected by the movable mirror 47 enters the polarizer 49 via the relay lens 48, and the light emitted from the polarizer 49 is used as probe light 6x, 6y, 6z. The positions of the movable mirror 47 and the relay lens 48 are the optical path length from the front focal point of the objective lens 23 to the principal point of the relay lens 48 and the optical path length from the principal point of the relay lens 48 to the movable mirror 47, respectively. It is determined so as to coincide with the focal length of the relay lens 48. The configurations of the epi-illumination optical system 2 and the detection optical system 3 of the Kerr effect microscope of FIG. 10 are the same as those of the Kerr effect microscope of FIG.

  The incident optical system 1A is configured to switch the optical path of the probe light by rotating the movable mirror 47. By appropriately determining the direction in which the movable mirror 47 faces, the light generated by the light source 41 is incident so that the optical axis thereof coincides with the optical axis of the objective lens 23. Thereby, the probe light 6z is incident in parallel to the z axis. As described above, the z component Mz of the magnetization M of the sample S can be specified by making the probe light 6z incident in parallel to the z axis. Hereinafter, the direction of the movable mirror 47 where the probe light 6z is incident in parallel to the z-axis is referred to as a basic direction.

  By rotating the movable mirror 47 about the z-axis from the basic direction, the light generated by the light source 41 deviates from the optical axis of the objective lens 23 on the body surface of the objective lens 23 and is on the x′-axis. (See FIG. 4A). Thereby, the probe light 6x is incident in a direction parallel to the zx plane and oblique to the z axis. As described above, the x component Mx of the magnetization M of the sample S can be specified by making the probe light 6x incident in a direction parallel to the zx plane and oblique to the z axis.

  Further, by rotating the movable mirror 47 about the x axis from the basic direction, the light generated by the light source 41 is shifted from the optical axis of the objective lens 23 on the body-fitted surface of the objective lens 23, and y 'The light is incident on a predetermined position defined on the axis (see FIG. 4B). Accordingly, the probe light 6y is incident in a direction parallel to the yz plane and oblique to the z axis. As described above, the y component My of the magnetization M of the sample S can be specified by making the probe light 6y incident in a direction parallel to the yz plane and oblique to the z axis.

  As described above, even in the configuration of the Kerr effect microscope of FIG. 10B, the three-dimensional direction of magnetization of the sample S, that is, the direction cosine of the magnetization M in the x, y, and z directions can be specified.

(Calibration of Kerr effect microscope)
In the Kerr effect microscope of FIGS. 1, 10A, and 10B, theoretically, the direction cosine of the magnetization M in the x direction, the y direction, and the z direction, that is, the direction of the magnetization M can be obtained as follows. it can. The relationship between the brightness of the captured image captured by the CCD camera 33 and the Kerr rotation angle of the reflected light is expressed by the following equation (1):
Here, theta is the angle from the extinction position of the analyzer 31, ± .theta.k is Kerr rotation angle of the reflected light of the sample S, a is the sensitivity of the CCD camera 33, E ² is the amount of light of the probe light Where F is the reciprocal of the extinction ratio of the detection optical system 3, t is the exposure time of the CCD camera 33, and D is the electrical offset of the CCD camera 33.

From equation (1), the luminance change ΔB caused by the Kerr effect of sample S is
It is expressed. In the range where θ and θk are small, and therefore can be approximated as sin2θ≈2θ and sin2θk≈2θk, the equation (2) is
It is expressed. Accordingly, it is possible to calculate the Kerr rotation angle θk of the reflected light from the luminance change ΔB and obtain the direction cosine of the magnetization M in the x, y, and z directions, that is, the direction of the magnetization M from the Kerr rotation angle θk. is there. Further, since the Kerr rotation angle θk of the reflected light and the ellipticity η of the reflected light are equivalent parameters corresponding one-to-one, the ellipticity η of the reflected light is calculated from the luminance change ΔB, and the magnetization is calculated from the ellipticity η. One skilled in the art will readily appreciate that direction cosines for M in the x, y, and z directions can be obtained.

However, depending on the adjustment status of the measurement system, the Kerr rotation angle θk (or ellipticity η) may not be obtained with sufficient accuracy. The expression (2 ′) includes many parameters, that is, the sensitivity a of the CCD camera 33, the light amount E ^{2 of the} probe light, the exposure time t of the CCD camera 33, and the angle θ from the extinction position of the analyzer 31. It is. The accuracy of the measurement system is not sufficient. For this reason, if the error of the parameter used to calculate the Kerr rotation angle θk (or ellipticity η) is large, the Kerr rotation angle θk (or ellipticity η), that is, The direction of the magnetization M cannot be obtained with sufficient accuracy.

  One way to overcome this difficulty is to perform an appropriate calibration. In the following, we will discuss how to calibrate the Kerr effect microscope.

  One preferred method is to acquire a correspondence relationship between the direction of the magnetization M and the brightness of the image captured by the CCD camera 33 in advance, and store correspondence data indicating the correspondence relationship in the arithmetic device 4. is there. The correspondence between the direction of the magnetization M and the luminance is obtained by using a thin film of magnetic material as a calibration sample and capturing a captured image with the CCD camera 33 while applying an external magnetic field to the calibration sample. Can do. If an external magnetic field large enough to saturate the magnetization of the calibration sample (ie, an external magnetic field larger than the coercive field of the magnetic material) is applied parallel to the xy plane, the magnetization M of the calibration sample. Can be oriented in a desired direction (parallel to the xy plane). If the captured images of the reflected lights 7x and 7y are acquired while changing the direction of the external magnetic field, the correspondence between the direction of the magnetization M and the brightness of the captured image of the CCD camera 33 can be obtained. When the magnetization direction of the sample S is actually measured, the direction of the magnetization M at each position of the sample S is calculated from the luminance of each pixel of the image captured by the CCD camera 33 and the corresponding data stored in the arithmetic unit 4. Is identified.

FIG. 11 is a graph showing the relationship between the direction of magnetization of the calibration sample and the brightness of specific pixels of the captured images of the reflected lights 7x and 7y obtained by sequentially changing the external magnetic field. Graph in Figure 11, when the direction of magnetization of the calibration sample coincides with the + x direction, theta _M is depicted as being zero. Since the positions of the optical paths of the probe lights 6x and 6y and the optical paths of the reflected lights 7x and 7y are different, the angle of magnetization of the brightness of the captured images of the reflected lights 7x and 7y depends on the adjustment status of the optical system. The average values B _x ^ave and B _y ^ave for θ _M and the luminance amplitudes B _x ^amp and B _y ^amp are different.

From the graph of FIG. 11, for each of the captured images of the reflected light 7x and 7y, average values B _x ^ave and B _y ^{ave of} luminance (in all directions of magnetization M) and luminance amplitudes B _x ^amp and B _y ^amp are obtained. Can be obtained. In other words, the luminance B _x of the specific pixel of the captured image of the reflected light 7x and the luminance B _{y of the} specific pixel of the captured image of the reflected light 7y can be approximated by the following equations:
B _x = B _x ^amp cos θ _M + B _x ^ave , (3a)
B _y = B _y ^amp sin θ _M + B _y ^ave , (3b)
Here, θ _M indicates the external magnetic field, that is, the magnetization direction of the calibration sample.

When the luminances B _x and B _y are normalized using the average values B _x ^ave and B _y ^ave and the amplitudes B _x ^amp and B _y ^amp , the direction of the magnetization M in the x direction as shown in FIG. The cosine α and the direction cosine β in the y direction are represented by the following formula:
α = cos θ _{M
^{= (B x -B x ave)}} / B x amp, ··· (3a ')
β = sin θ _M
= (B _y -B _y ^ave ) / B _y ^amp . ... (3b ')

Expressions (3a ′) and (3b ′) indicate the relationship between the luminance of the captured images of the reflected lights 7x and 7y and the direction cosine α in the x direction and the direction cosine β in the y direction of the magnetization M. That is, by measuring the sample S, the reflected light 7x, when the luminance of a specific pixel of the captured image 7y were B _x, B _y, the magnetization direction of the magnetization M at a position corresponding to the specific pixel of the sample S The direction cosine α in the x direction of M and the direction cosine β in the y direction can be obtained by equations (3a ′) and (3b ′). In other words, by using the expressions (3a ′) and (3b ′), the direction of the magnetization M at each position of the sample S can be obtained from the luminance of each pixel of the captured images of the reflected light 7x and 7y.

Other suitable calibration method uses a reflective Faraday glass such as illustrated in FIG. 13 as a calibration sample S _C, thereby, the Kerr rotation angle .theta.k (or ellipticity eta) and the luminance of the captured image This is a method of previously measuring the correspondence relationship. In this embodiment, the calibration sample S _C is composed of a Faraday glass plate 61 and the aluminum thin film 62. The aluminum thin film 62 functions as a mirror that reflects light incident on the Faraday glass plate 61. The probe light is incident on the Faraday glass plate 61 and further reflected by the aluminum thin film 62, whereby reflected light is generated.

By the Faraday effect which is expressed in the calibration sample S _C, the rotation angle of the deflecting surface of the reflected light (Faraday rotation angle) is represented by the following formula:
Here, V is the Verde constant of the Faraday glass plate 61, d is the thickness of the Faraday glass plate 61, and H is the magnitude of the magnetic field applied in the normal direction of the Faraday glass plate 61. , Α is the refraction angle of the probe light inside the Faraday glass plate 61. It should be noted that the Faraday rotation angle θ _F of the reflected light does not depend on the incident angle of the probe light. The Faraday rotation angle θ _F is determined only by the Verde constant V and the thickness d of the Faraday glass plate 61 and the magnetic field H applied in the normal direction of the Faraday glass plate 61. Therefore, measured in advance Verdet constant V and the thickness d of the Faraday glass plate 61, further, by applying a known magnetic field H in the normal direction of the Faraday glass plate 61, reflected by the known Faraday rotation angle theta _F The light deflection surface can be rotated.

If this is utilized, the correspondence between the Kerr rotation angle θk of the reflected light and the brightness of the captured image can be measured in advance. That is, the deflecting surface of the reflected light incident probe light to a desired Faraday rotation angle theta _F only calibrated while applying a magnetic field H such as to rotate sample S _C, by measuring the luminance of the captured image in this case, rotation angle of the deflecting surface of the reflected light can know the brightness of the captured image when a theta _F. By performing the same measurement while changing the magnetic field H, it is possible to know the correspondence between the rotation angle of the deflection surface of the reflected light and the brightness of the captured image. Since the correspondence relationship between the rotation angle of the deflecting surface of the reflected light and the brightness of the captured image is the correspondence relationship between the Kerr rotation angle θk of the reflected light and the brightness of the captured image, the Kerr rotation angle θk is determined by the above measurement. Correspondence data indicating the correspondence between the brightness of the captured image and the captured image can be obtained. By using this correspondence data, the Kerr rotation angle θk by the sample S can be known from the brightness of the captured image. If the correspondence data between the Kerr rotation angle θk and the brightness of the captured image is measured in advance for each of the reflected lights 7x, 7y, and 7z, the Kerr rotation angle θk is determined from the brightness of the captured images of the reflected lights 7x, 7y, and 7z. It is possible to specify with high accuracy and further specify the direction cosine of the magnetization M of the sample S in the x direction, the y direction, and the z direction from the Kerr rotation angle θk.

(Corresponding to Faraday effect of objective lens)
In the Kerr effect microscopes of FIGS. 1, 10A, and 10B, when an external magnetic field is applied to the sample S, the deflection surfaces of the probe light and the reflected light may rotate in the objective lens 23 due to the Faraday effect. More specifically, referring to FIG. 14, when an external magnetic field is applied to the sample S by the external magnetic field applying electromagnet 53, the lens L _{1 of the} objective lens 23, in particular, directly facing (that is, closest to) the sample S. A leakage magnetic field _HL can be applied to the. In many cases, the leakage magnetic field H _L has a component Ha in the traveling direction of the probe light or reflected light, and the lens L ₁ is often a glass that exhibits a Faraday effect although it is small. Made of. Therefore, the deflection surfaces of the probe light and the reflected light can rotate due to the Faraday effect. The rotation angle (Faraday rotation angle) θ _F1 of the deflection surface of the probe light and the reflected light by the lens L ₁ is expressed by the following equation:
θ _F1 = V _L1 · Ha · d ₁ , (5)
Here, V _L1 is the Verde constant of the lens L ₁ , Ha is the component of the leakage magnetic flux in the traveling direction of the probe light or reflected light, and d ₁ is a position at which the probe light or reflected light passes. lens _{L 1} is the thickness. In the detection optical system 3, and the Faraday rotation angle theta _F1 by the lens L _1, because where the Kerr rotation angle θk by the sample S is observed are superimposed, the presence of the Faraday rotation angle theta _F1 by a lens L _1, according to the sample S This hinders accurate measurement of the Kerr rotation angle θk.

In order to cope with such a problem, it is preferable to provide a correction electromagnet 54 that cancels the rotation of the polarization plane due to the Faraday effect of the lens L _{1 in} the vicinity of the other lens L ₂ of the objective lens 23. By applying a magnetic field to the lens L ₂ using the correction electromagnet 54 to cause the lens L ₂ to exhibit a Faraday effect, the rotation of the polarization plane due to the Faraday effect of the lens L ₁ is changed, and the polarization plane due to the Faraday effect of the lens L ₂ is changed. Can be countered by rotation. Thereby, the Kerr rotation angle θk by the sample S can be accurately measured.

To appropriately control the Faraday rotational angle of the lens L _2, it is necessary to appropriately control the drive current supplied to the correction electromagnet 54. FIG. 15 shows an example of a suitable control system for the drive current supplied to the correction electromagnet 54 when the leakage magnetic field _HL is proportional to the drive current supplied to the external magnetic field application electromagnet 53. In the configuration of FIG. 15, a drive current is supplied to the external magnetic field application electromagnet 53 by the magnetic field application electromagnet amplifier 55, and a drive current is supplied to the correction electromagnet 54 by the correction electromagnet amplifier 56. The control computer 57 supplies an external magnetic field control signal 58 having a voltage level proportional to the drive current to be supplied by the magnetic field application electromagnet amplifier 55 to the magnetic field application electromagnet amplifier 55. The voltage divider 59 divides the external magnetic field control signal 58 to generate a corrected electromagnet control signal 60. The correction electromagnet amplifier 56 supplies a drive current corresponding to the voltage level of the correction electromagnet control signal 60 to the correction electromagnet 54.

According to such a configuration, a driving current proportional to the driving current supplied to the external magnetic field applying electromagnet 53, that is, a driving current proportional to the leakage magnetic field _HL is caused to flow through the correction electromagnet 54. it is possible to properly control the Faraday rotational angle in L _2.

On the other hand, FIG. 16 shows an example of a suitable control system for the current supplied to the correction electromagnet 54 when the leakage magnetic field _HL is not proportional to the drive current supplied to the external magnetic field application electromagnet 53. A correspondence relationship between an external magnetic field applied to the sample S (that is, a drive current that flows through the external magnetic field application electromagnet 53) and a drive current that should flow through the correction electromagnet 54 is measured in advance, and the correspondence relationship is controlled as table data. Stored in the computer 57. The control computer 57 determines a drive current to be supplied to the correction electromagnet 54 from the external magnetic field to be applied to the sample S and the table data, and outputs a correction electromagnet control signal 60 indicating the drive current to the correction electromagnet amplifier 56. To supply. The correction electromagnet amplifier 56 supplies a drive current corresponding to the voltage level of the correction electromagnet control signal 60 to the correction electromagnet 54.

According to such a configuration, an appropriate drive current corresponding to the external magnetic field applied to the sample S is supplied to the correction electromagnet 54, thereby, it is possible to appropriately control the Faraday rotational angle of the lens L _2.

The inventor has confirmed by experiments that the Faraday effect in the lens L ₁ can be canceled by passing a current through the correction electromagnet 54. FIG. 17 is a graph showing the relationship between the external magnetic field and the luminance of a predetermined pixel of the captured image captured by the CCD camera 33 when a ruthenium thin film is used as the sample S.

Since ruthenium is a nonmagnetic material, the sample S does not exhibit the Kerr effect. Therefore, the luminance should not change even when an external magnetic field is applied. However, in practice, (correction if not passed a driving current to the electromagnet 54) varies the brightness by the Faraday effect in the lens L ₁ of the objective lens 23.

Such a change in luminance can be suppressed by passing a drive current through the correction electromagnet 54. In the inventor's experimental system, when an external magnetic field of 2000 (Oe) is applied to the sample S, the brightness due to the application of the external magnetic field is adjusted by adjusting the control system so that a drive current of 47 mA flows through the correction electromagnet 54. Was suppressed. This is by expressing the Faraday effect in the lens L ₂ by flowing a drive current to the correction electromagnet 54 have shown that it is possible to cancel the rotation of the polarization plane by the Faraday effect of the lens L _1.

FIG. 1 is a diagram showing a configuration of a Kerr effect microscope according to an embodiment of the present invention. FIG. 2 is a diagram showing the incident direction of the probe light and the reflected direction of the reflected light in the Kerr effect microscope of FIG. FIG. 3 is a diagram showing the incident direction of the probe light and the reflected direction of the reflected light in the Kerr effect microscope of FIG. FIG. 4 is a diagram showing the incident position of the probe light on the body-mounted surface of the objective lens. FIG. 5 is a diagram illustrating an example of a display image displayed on the display device. FIG. 6A is a diagram illustrating the operation timing of the Kerr effect microscope when the three-dimensional direction of magnetization is displayed as a moving image. FIG. 6B is a diagram illustrating the operation timing of the Kerr effect microscope when the two-dimensional direction of magnetization is displayed as a moving image. FIG. 7A is a graph showing an example of a magnetization curve in the x direction acquired by the Kerr effect microscope of FIG. FIG. 7B is a graph showing an example of a magnetization curve in the y direction acquired by the Kerr effect microscope of FIG. FIG. 8 is a bird's-eye view showing an example of the configuration of the external magnetic field application device. FIG. 9 is a graph showing an example of the intensity waveform of the double-modulated probe light. FIG. 10A is a diagram showing another configuration of the Kerr effect microscope of the present invention. FIG. 10B is a diagram showing still another configuration of the Kerr effect microscope of the present invention. Figure 11 is a graph showing the direction theta _M magnetization, the correspondence relationship between the brightness in the captured image. Figure 12 is a direction theta _M of the magnetization, x component of the unit vector in the direction of magnetization is a graph showing the relationship between the y-component. FIG. 13 is a diagram for explaining a technique for calibrating a Kerr effect microscope using a reflection type Faraday glass. FIG. 14 is a diagram showing a configuration of a Kerr effect microscope for canceling the Faraday effect generated when the leakage magnetic flux of the external magnetic field applying electromagnet is applied to the objective lens. FIG. 15 is a diagram illustrating a configuration of a control system for canceling the Faraday effect generated when leakage magnetic flux is applied to the objective lens. FIG. 16 is a diagram showing another configuration of the control system for canceling the Faraday effect generated when leakage magnetic flux is applied to the objective lens. FIG. 17 is a graph of experimental data showing that the Faraday effect generated when leakage magnetic flux is applied to the objective lens can be canceled by applying a magnetic field to the objective lens with the correction electromagnet.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1A: Incident optical system 2: Epi-illumination optical system 3: Detection optical system 4: Calculation apparatus 5: Display apparatus 6x, 6y, 6z: Probe light 7x, 7y, 7z: Reflected light 11x, 11y, 11z, 11: Laser Diode 12x, 12y, 12z: Lens 13, 14: Mirror 15, 16: Half mirror 17: Polarizer 18x, 18y, 18z: Laser light 19x, 19y, 19z: Shutter 21: Smith mirror 22: Half mirror 23: Objective lens 31: Analyzer 32: Imaging lens 33: CCD camera 41: Light source 42: Condenser lens 43: Aperture stop 44: Field stop 45: Collimator lens 46: Mirror 47: Movable mirror 48: Relay lens 49: Polarizer 51: x Shaft electromagnet 52: y-axis electromagnet 53: external magnetic field applying electromagnet 54: correction electromagnet 55: magnetic field Pressurized electromagnet amplifier 56: Correction electromagnet amplifier 57: the control computer 58: External magnetic field control signal 59: divider 60: Correction electromagnet control signal S: Sample S _C: Calibration Sample

Claims (25)

Probe light incident means configured to allow the first probe light to be incident on the sample in the first direction and to allow the second probe light to be incident in a second direction different from the first direction;
The sample at each position of the sample from the first reflected light generated by reflecting the first probe light by the sample and the second reflected light generated by reflecting the second probe light by the sample. the direction of magnetization in the plane of the surface of the to and a magnetization direction specifying means for specifying,
The first direction is defined obliquely with respect to a vertical direction perpendicular to the surface of the sample, in a plane of a first plane perpendicular to the surface of the sample,
The Kerr effect microscope , wherein the second direction is defined obliquely with respect to the vertical direction in a plane of a second plane perpendicular to the first plane . The Kerr effect microscope according to claim 1,
Before SL magnetization direction specifying means, the magnetization of the sample, to identify the direction cosine of the direction in the first plane and the plane of both surfaces of the sample from the first reflected light, the said sample A Kerr effect microscope for identifying a direction cosine of magnetization in a direction in both the second plane and the surface of the sample from the second reflected light. The Kerr effect microscope according to claim 2 ,
The probe light incident means is configured to allow the third probe light to be incident in the vertical direction ,
The magnetization direction specifying means adds the three-dimensional direction of the magnetization of the sample to the first reflected light and the second reflected light, and the third probe light is generated by being reflected by the sample. 3 Kerr effect microscope specified from reflected light. The Kerr effect microscope according to claim 3 ,
Before SL magnetization direction specifying means before Symbol third reflected light, the magnetization of the sample, Kerr effect microscope to identify the direction cosines for the vertical direction. The Kerr effect microscope according to claim 1,
The Kerr effect microscope, wherein the probe light incident means is configured to incident the first probe light and the second probe light on the sample in a time-sharing manner. The Kerr effect microscope according to claim 1,
The probe light incident means includes
A first semiconductor laser for generating a first laser beam used for generating the first probe light;
A Kerr effect microscope comprising: a second semiconductor laser that generates a second laser beam used to generate the second probe beam. The Kerr effect microscope according to claim 6 ,
The probe light incident means further includes:
A first shutter that passes or blocks the first laser light;
A second shutter that passes or blocks the second laser light,
The first shutter and the second shutter pass through the first laser light and the second laser light, respectively, so that the first probe light and the second probe light are incident on the sample in a time division manner. , Or cut off the Kerr effect microscope. The Kerr effect microscope according to claim 1,
A Kerr effect microscope in which each of the first probe light and the second probe light is doubly modulated. The Kerr effect microscope according to claim 1,
Furthermore,
Comprising a display device;
The Kerr effect microscope, wherein the magnetization direction specifying means displays a display image indicating a magnetization direction at each position of the sample on the display device. The Kerr effect microscope according to claim 9,
Furthermore,
An external magnetic field application device for applying a variable external magnetic field to the sample;
The magnetization direction specifying means sequentially specifies the magnetization direction at each position of the sample while the external magnetic field is changed by the external magnetic field application device, and displays the specified magnetization direction as a moving image. Car effect microscope displayed on the device. The Kerr effect microscope according to claim 2,
Furthermore,
An external magnetic field application device for applying a variable external magnetic field to the sample;
From the correspondence relationship between the Kerr rotation angle or ellipticity of the first reflected light and the external magnetic field, a magnetization curve is obtained for directions in the planes of both the first plane and the surface of the sample. A Kerr effect microscope comprising a magnetization curve measuring means. The Kerr effect microscope according to claim 1,
The probe light incident means includes
A single light source,
A Kerr effect microscope comprising: a deflection mechanism that generates the first probe light and the second probe light by switching an optical path of light generated by the light source. The Kerr effect microscope according to claim 1,
The magnetization direction specifying means includes
An imaging device for acquiring captured images of the first reflected light and the second reflected light;
An arithmetic unit that identifies the direction of magnetization in the surface of the sample at each position of the sample from the captured image;
The arithmetic unit stores in advance correspondence data indicating a correspondence relationship between the luminance of each pixel in the captured image and the direction of magnetization in the surface of the sample at each position of the sample, and the captured image A Kerr effect microscope that identifies the direction of magnetization in the surface of the sample at each position of the sample from the brightness of each pixel and the corresponding data. The Kerr effect microscope according to claim 1,
The magnetization direction specifying means includes
An imaging device for acquiring captured images of the first reflected light and the second reflected light;
An arithmetic unit that identifies the direction of magnetization in the surface of the sample at each position of the sample from the captured image;
The arithmetic device stores in advance correspondence data indicating a correspondence relationship between the luminance of each pixel in the captured image and the Kerr rotation angle or ellipticity of the first reflected light and the second reflected light, and the captured image The Kerr rotation angle or ellipticity of the first reflected light and the second reflected light is specified from the luminance of each pixel and the corresponding data, and at each position of the sample from the specified Kerr rotation angle or ellipticity. A Kerr effect microscope for specifying the direction of magnetization in the plane of the surface of the sample . The Kerr effect microscope according to claim 1,
Furthermore, an external magnetic field application device for applying an external magnetic field to the sample is provided,
The probe light incident means includes
An objective lens that makes the first probe light and the second probe light incident on the sample, and makes the first reflected light and the second reflected light reflected by the sample incident on the magnetization direction specifying means;
A Kerr effect microscope comprising: a Faraday effect correction device for canceling a Faraday effect caused by a leakage magnetic field applied to the objective lens by the external magnetic field application device. The Kerr effect microscope according to claim 15,
The objective lens is
A first lens that directly faces the sample and through which the first probe light, the second probe light, the first reflected light, and the second reflected light pass;
A second lens through which the first probe light, the second probe light, the first reflected light, and the second reflected light pass;
The Faraday effect correction device includes a correction electromagnet that applies a correction magnetic field to the second lens. The Kerr effect microscope according to claim 16,
The Faraday effect correction device further includes drive current supply means for supplying a drive current to the correction electromagnet,
The driving current supply means is a Kerr effect microscope that supplies the driving current to the correction electromagnet according to the external magnetic field generated by the external magnetic field application device. Injecting the first probe light into the sample in the first direction;
Incident second probe light in a second direction different from the first direction;
The sample at each position of the sample from the first reflected light generated by reflecting the first probe light by the sample and the second reflected light generated by reflecting the second probe light by the sample. Identifying the direction of magnetization in the plane of the surface of
The first direction is defined obliquely with respect to a vertical direction perpendicular to the surface of the sample, in a plane of a first plane perpendicular to the surface of the sample,
The magnetization direction measuring method in which the second direction is defined obliquely with respect to the vertical direction in a plane of a second plane perpendicular to the first plane . The magnetization direction measuring method according to claim 18 ,
Furthermore,
Providing a third probe light in the vertical direction ;
3-dimensional direction of magnetization in each position of the sample, in addition to the first reflected light and the second reflected light, identified from the third reflected light and the third probe light is generated is reflected by the sample Magnetization direction measuring method. The magnetization direction measuring method according to claim 18 ,
Specifying the direction of magnetization in the plane of the surface of the sample at each position of the sample ,
Obtaining captured images of the first reflected light and the second reflected light;
Identifying the direction of magnetization in the plane of the surface of the sample at each position of the sample from the captured image,
The magnetization direction measuring method further includes a step of preparing correspondence data indicating a correspondence relationship between the luminance of each pixel in the captured image and the direction of magnetization in the surface of the sample at each position of the sample. And
The direction of magnetization in the surface of the sample at each position of the sample is specified from the luminance of each pixel in the captured image and the corresponding data. The magnetization direction measuring method according to claim 20 ,
The step of preparing the correspondence data includes:
An external magnetic field larger than the coercive field of the magnetic material is applied to the calibration sample including a thin film of the magnetic material.
Changing the direction of magnetization of the magnetic material by applying while changing the direction; and
Injecting the first calibration probe light and the second calibration probe light into the calibration sample while the magnetization direction of the magnetic material is changed;
Obtaining captured images of the first calibration reflected light and the second calibration reflected light generated by reflecting the first calibration probe light and the second calibration probe light by the calibration sample;
And generating the corresponding data from the luminance of the captured image of the first calibration reflected light and the second calibration reflected light. The magnetization direction measuring method according to claim 18 ,
Specifying the direction of magnetization in the plane of the surface of the sample at each position of the sample ,
Obtaining captured images of the first reflected light and the second reflected light;
Identifying the direction of magnetization in the plane of the surface of the sample at each position of the sample from the captured image,
The magnetization direction measurement method further includes a step of preparing correspondence data indicating a correspondence relationship between the luminance of each pixel in the captured image and the Kerr rotation angle or ellipticity of the first reflected light and the second reflected light. And
The direction of magnetization in the surface of the sample at each position of the sample is specified from the luminance of each pixel in the captured image and the corresponding data. The magnetization direction measuring method according to claim 22 ,
The step of preparing the correspondence data includes:
Applying a magnetic field to a calibration sample including a Faraday glass plate expressing a Faraday effect while changing the strength of the magnetic field in a direction perpendicular to the Faraday glass plate;
Injecting the first calibration probe light and the second calibration probe light into the calibration sample while the magnetic field is applied;
Obtaining captured images of the first calibration reflected light and the second calibration reflected light generated by reflecting the first calibration probe light and the second calibration probe light by the calibration sample;
And a step of generating the correspondence data from luminances in captured images of the first calibration reflected light and the second calibration reflected light. A calibration method for calibrating the Kerr effect microscope according to claim 13 or 14,
Changing the direction of magnetization of the magnetic material by applying an external magnetic field larger than the coercive field of the magnetic material to a calibration sample including a thin film of the magnetic material while changing the direction;
Injecting the first calibration probe light and the second calibration probe light into the calibration sample while the magnetization direction of the magnetic material is changed;
Obtaining captured images of the first calibration reflected light and the second calibration reflected light generated by reflecting the first calibration probe light and the second calibration probe light by the calibration sample;
From the brightness of the captured image of the first calibration reflected light and the second calibration reflected light, and generating the corresponding data indicating the direction of the correspondence between the magnetization intensity of each pixel in the captured image A Kerr effect microscope calibration method. A calibration method for calibrating the Kerr effect microscope according to claim 13 or 14,
Applying a magnetic field to a calibration sample including a Faraday glass plate expressing a Faraday effect while changing the strength of the magnetic field in a direction perpendicular to the Faraday glass plate;
Injecting calibration probe light into the calibration sample while the magnetic field is applied;
Obtaining a captured image of the reflected light for calibration generated by reflecting the calibration probe light by the calibration sample;
From the luminance in the captured image of the calibration reflected light, the Kerr effect microscope calibration method comprising the step of generating the corresponding data indicating a correspondence relationship between the Kerr rotation angle of the luminance and the reflected light of each pixel in the captured image .