JPS597183B2 - electronic microscope - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electron microscope suitable for observing magnetic domains by applying an alternating magnetic field to a magnetic sample.

A magnetic sample to which a magnetic field has recently been applied is observed with an electron microscope,
Much work has been done to obtain knowledge regarding magnetic domain structure, etc.

However, conventionally, the magnetic field applied to the sample is a static magnetic field, and an electron microscope is used to observe how the magnetic domains of the sample move when an alternatingly changing magnetic field is applied to the sample. None existed, and the emergence of such an electron microscope was awaited.

The present invention has been made in response to these demands, and it is a method of separating and displaying magnetic domain images in each magnetic field application state when an alternating magnetic field whose intensity changes in a rectangular pulse shape is applied to a sample. DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a drawing for showing one embodiment of the present invention. In the drawing, 1 is an electron gun, and an electron beam 2 generated from the electron gun 1 enters a converging lens 3 and becomes a parallel beam. It is incident on the magnetic sample 5 along the axis 4.

Reference numeral 6 denotes a coil for applying a magnetic field to the sample 5, and the coil 6 is supplied with a voltage such as 'P' as shown in FIG. 2a from a power source 7.
A square wave current of IKHz is supplied.

Therefore, from the magnetic field applying coil 6, an alternating magnetic field whose magnetic field intensity changes periodically in a rectangular pulse shape such as H, O, -H as shown in FIG. 2B is applied to the sample.

The electron beam transmitted through the sample 5 is influenced by the magnetic field created by the magnetic field applying coil 6.

That is, during the period indicated by B in FIG. 2b, the electron beam 2 travels straight along the optical axis 4 without being deflected at all by the magnetic field created by the coil 6, but during the period indicated by A in FIG. During the period when the magnetic field H is applied, it is deflected as shown by the locus A, and during the period when the magnetic field H is applied, which is indicated by C in Fig. 2b, it is deflected in the opposite direction to the locus I, like the trajectory mouth. be done.

Reference numeral 1 denotes a correction magnetic field applying means for causing the electron beam that has undergone such a deflection to travel on the optical axis again. 1. It consists of second correction coils 9a and 9b.

The first and second correction coils 9at9b are connected in the opposite direction and the same direction as the connection direction of the magnetic field applying coil 6, respectively.

Therefore, the first correction coil 9a generates a magnetic field having an opposite phase to the magnetic field strength waveform shown in FIG. 2B, as shown in FIG.
The second compensation coil 9b generates a compensation magnetic field having the same phase as that in FIG. 2b.

Therefore, for example, the electron beam deflected by the magnetic field applying coil 6 as shown in the above-mentioned trajectory A is now deflected in the direction toward the optical axis 4 by the first correction coil 9a, and is further deflected by the second correction coil 9a.
is directed along the optical axis 4 by the correction coil 9b.

In this way, the optical axis 4 is always
The electron beam is caused to travel along the objective lens 10.
incident on .

At the rear stage of the objective lens 10, there is a power source connected to the power source 7 as shown in FIG.
An image separation coil 11 to which a rectangular pulsed current as shown in FIG.

Of course, other imaging lenses may be arranged after the objective lens 10.

In this way, the image separation coil 11 generates a rectangular pulsed magnetic field that is completely synchronized with the magnetic field applied to the sample 5, as shown in FIG. 2b.

Therefore, during the period when a magnetic field of strength H is applied to the sample 5 indicated by A in FIG. The electrons projected at the position 2 and passed through the sample 5 during the period when no magnetic field was applied to the sample 5 and during the period when a magnetic field of strength -H was applied to the sample 5, respectively, as shown by B and C in Fig. 2b. The line is ``
It is projected to the position of and.

As a result, when the photographic film 12 is developed, the magnified image obtained by the objective lens 11 when an alternating magnetic field is applied to the sample 5 in the order of intensity H, 0, -H is the photographic film 12.
2, each applied magnetic field is separated and recorded as three types of images with different applied magnetic fields, and by comparing and contrasting these three types of images, the movement of magnetic domains between these magnetic field application states can be observed. be able to.

In the embodiment described above, the magnetic field applied to the sample is H
, 0, -H, but the same applies when applying a magnetic field that alternatingly changes H, -H or H, 0 to the sample. It can be implemented.

It is also possible to change the frequency of the alternating magnetic field and observe the movement of the magnetic domains.
It is also possible to correct the deflection of the electron beam due to the alternating magnetic field even if it is placed above the sample.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing one embodiment of the present invention, and FIG. 2 is a diagram showing the current waveforms supplied to each coil of the embodiment device shown in FIG. 1 and the magnetic field generated by the coils. It is. 1: Electron gun, 2: Electron beam, 3: Converging lens, 4: Optical axis,
5: sample, 6: magnetic field application coil, 7: power supply, fl: correction magnetic field application means, 9a, 9b: correction coil, 10: objective lens, 11: image separation coil, 12: photographic film.

Claims (1)

[Claims] 1. An electron gun, a converging lens for converging an electron beam generated from the electron gun onto a sample, means for applying a magnetic field whose intensity changes in a rectangular pulse shape to the sample, and an electron beam generated by the means. a correction means for correcting the deflection of the beam; an objective lens into which the electron beam corrected by the correction means is incident; An electron microscope characterized in that it comprises a means for deflecting an electron beam.