JP7041876B2 - Magnetic anisotropy evaluation device, magnetic anisotropy evaluation method and calculation mechanism - Google Patents

Description

Application of Article 30, Paragraph 2 of the Patent Act On February 14, 2018, "Applied Physics" of the Japan Society of Applied Physics published on the website (http://doi.org/10.7567/APEX.11.033002). Announced at "Express 11,033002"

The present invention relates to a magnetic anisotropy evaluation device and a magnetic anisotropy evaluation method for a magnetic material, and more particularly to a technique for evaluating magnetic anisotropy using a torque curve.

The magnetic anisotropy of a magnetic material is, for example, a characteristic known in magnetic recording media. That is, the particle size of the magnetic crystal grains in the magnetic recording layer is reduced in order to increase the density of magnetic recording in the magnetic recording medium. The reduction in the grain size of the magnetic crystal grains reduces the thermal stability of the recorded magnetization (signal). Therefore, in order to compensate for the decrease in thermal stability due to the reduction in the particle size of the magnetic crystal grains, the magnetic crystal grains are formed using a material having higher magnetic anisotropy. As a result, the magnetic recording layer of the magnetic recording medium has magnetic anisotropy.

An _L10 type ordered alloy has been proposed as a material having a relatively large magnetic anisotropy. Patent Document ₁ contains an L10 type rule containing at least one element selected from the group consisting of Fe, Co and Ni and at least one element selected from the group consisting of Pt, Pd, Au and Ir. The alloy is listed. Typical L10 type ordered alloys include FePt, CoPt, FePd, _CoPd and the like.

Further, Patent Document 1 describes a method of using a granular structure in which magnetic crystal grains are surrounded by non-magnetic crystal grain boundaries such as oxides and nitrides as a method for increasing the density of the magnetic recording layer. Proposed.

Patent Document 2 describes a configuration in which a magnetic thin film (thin film of a magnetic material) is used as a granular film by interposing a non-magnetic substance between crystal grains of an alloy. Examples of the non-magnetic material used for forming this granular film include SiO ₂ , Cr ₂ O ₃ , ZrO ₂ , Al ₂ O ₃ and the like. These non-magnetic substances have a high possibility of magnetically separating the crystal grains of the Co—Pt—C based alloy.

Patent Document 3 describes a magnetic thin film having a granular structure. This granular structure is a ferromagnetic crystal grain whose main component is a Co-M-Pt alloy having an ordered structure of L11 _type atoms (M indicates a single or a plurality of metal elements other than Co and Pt). And a non-magnetic grain boundary surrounding the ferromagnetic crystal grains. The alloy is a ternary ordered alloy such as CoFePt having a granular structure.

Conventionally, the evaluation of the magnetic anisotropy of a magnetic material as described above has been performed by directly measuring the magnetic torque curve. Specifically, for example, as shown in the following equation (1), the component of the magnetic anisotropy energy as a descriptive element is obtained from the obtained magnetic anisotropy (curve) T, and the magnetic anisotropy constant is obtained based on these components. Ask. Then, the magnetic anisotropy is evaluated by this constant. A method for measuring a magnetic torque curve is described in, for example, Non-Patent Document 1. This method mechanically measures the magnetic torque generated when a magnetic field is applied to a magnetic thin film.

T =-(K _u1 + K _u2 ) sin2θ _M + (K _u2 / 2) sin4θ _M equation (1)

here,
K _u1 : First component of magnetic anisotropy energy (primary component)
K _u2 : Second component of magnetic anisotropy energy (secondary component)
θ _M : Easy axis of magnetization and angle formed by magnetization Note that the magnetic torque means that when a magnetic field is applied to a sample and the sample is magnetized, its internal magnetization points in the direction of the magnetic field. That is, it is a rotational force acting on the sample so that the easy magnetization direction tends toward the magnetic field. The magnetic torque curve is the relationship between the magnetic field direction (magnetic field angle) and the magnetic torque.

International Publication No. 2013/140469 Japanese Unexamined Patent Publication No. 2010-135610 Japanese Unexamined Patent Publication No. 2010-34182

Physics of Ferromagnets (Bottom) Satoshi Short Angle Shokabo, pp. 10-21 (1984)

However, in the above-mentioned method for measuring magnetic torque, it is difficult to measure magnetic torque accurately due to the influence of demagnetizing force from the sample substrate and the measuring holder and the influence of measurement noise. As a result, a large error may occur in the evaluation of magnetic anisotropy.

The present invention has been made in view of the above-mentioned problems, and an object thereof is a magnetic anisotropy evaluation device and a magnetic anisotropy capable of accurately evaluating magnetic anisotropy in a magnetic thin film. The evaluation method is to be provided.

An example of the means for solving the problem of the present invention is a mechanism for measuring the hole resistance of a magnetic material of a thin film having a flat flat surface, a mechanism for applying a magnetic field to the magnetic material, and a mechanism for applying a magnetic field to the magnetic material, and the hole resistance of the magnetic material. It is characterized by having a first calculation for calculating a magnetic torque curve and a second calculation mechanism for calculating a magnetic anisotropy constant from the calculated magnetic torque curve from the dependence on the applied magnetic field angle. It is a magnetic anisotropy evaluation device.

Another example of the means for solving the problem of the present invention is to read the magnetic field applied from the magnetic field application mechanism of the magnetic anisotropy evaluation device with a Hall sensor, and compare the applied magnetic field strength and the read magnetic field strength to the magnetic field direction. The magnetic anisotropy evaluation device equipped with the angle measuring mechanism and the magnetic anisotropy evaluation device are used to derive the applied magnetic field angle dependence of the normal Hall resistance and the magnetic resistance, and the normal Hall resistance and the magnetism are obtained. Using the applied magnetic field angle dependence of the resistance, the normal Hall resistance component and the magnetic resistance component are separated from the measurement result of the Hall resistance of the magnetic material, and the applied magnetic field angle dependence of the abnormal Hall resistance component of the magnetic material is derived, and the abnormality is obtained. This is a magnetic anisotropy evaluation method for evaluating the magnetic anisotropy of a magnetic material using the dependence of the Hall resistance component on the applied magnetic field angle.

As an example of the magnetic anisotropy analysis means, in the step of calculating the magnetic anisotropy constant from the magnetic torque curve, fitting by the magnetic torque curve is used as a means for evaluating the magnetic anisotropy of the magnetic material. This is a method for evaluating magnetic anisotropy.

By adopting the above-mentioned magnetic anisotropy evaluation device and magnetic anisotropy evaluation method, it is possible to reduce the influence of the demagnetizing field from the sample substrate and the measurement holder and the measurement noise, so that it is difficult to evaluate by the conventional method. It becomes possible to accurately evaluate the magnetic anisotropy of a magnetic material.

It is a figure which shows the magnetic anisotropy evaluation apparatus in this embodiment. It is a figure of the arrangement of the sample holder, the sample and the Hall sensor in this embodiment. It is a flowchart which shows the calculation method in this embodiment. It is a graph which shows the measurement result of the magnetic field angle dependence of Hall resistance in Example 1 of this invention. It is a graph which shows the measurement result of the magnetic field strength dependence of Hall resistance in Example 1 of this invention. It is a graph which shows the measurement result of the magnetic field angle dependence of Hall resistance in Example 2 of this invention. It is a graph which shows the magnetic torque curve in the comparative example of this invention.

Hereinafter, the form of the magnetic anisotropy evaluation device and the magnetic anisotropy evaluation method of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the description of the embodiments shown below, and it is obvious to those skilled in the art that the form and details can be variously changed without departing from the spirit of the invention disclosed in the present specification and the like. .. In addition, the configurations according to different embodiments and examples can be combined and implemented as appropriate.

The magnetic anisotropy evaluation device according to the embodiment of the present invention is obtained by measuring the electric resistance due to the Hall effect, that is, the Hall resistance, instead of measuring the magnetic torque mechanically. That is, the magnetic torque T can also be expressed by the following equation (2) described by the angle formed by the easy axis of magnetization and the direction of magnetization, and the magnetization angle θ _M of this equation (2) is measured for Hall resistance. By doing so, the magnetic torque (curve) is finally obtained. The angle formed by the easy axis of magnetization and the direction of magnetization is hereinafter also referred to as "magnetization angle" or "magnetization angle". More specifically, in the equation (2), the relationship of the magnetization angle θ _M with respect to the magnetic field angle θ _H is obtained by measuring the magnetic field angle dependence and the magnetic field strength dependence of the Hall resistance of the sample 3, and finally. Find the magnetic torque curve. The magnetic field angle dependence can be referred to as an applied magnetic field angle dependence, and the magnetic field strength dependence can be referred to as an applied magnetic field strength dependence.

T = HM _s sin (θ _H − θ _M ) Equation (2)
here,
H: Magnetic field strength M _s : Saturation magnetization θ _H : Magnetic field angle In other words, the angle of the applied magnetic field θ _M : Magnetization angle In other words, the angle formed by the easy axis of magnetization and the magnetization direction The Hall resistance is given in the equation (3) described later. As shown, it can be represented by components such as the normal Hall effect (NHE) component and the abnormal Hall effect (AHE) component. These components can be obtained by the method described later, and the magnetization angle θ _M can be obtained.

This Hall resistance is generated in a direction orthogonal to the current and magnetization applied to the magnetic material. Hall resistance can be measured by performing 4-terminal measurement in which voltage terminals and current terminals are arranged orthogonally to the surface of a magnetic thin film as a magnetic material. Further, the resistance due to the anomalous Hall effect, that is, the anomalous Hall resistance _RAHE is proportional to the magnitude of the magnetization orthogonal to the current. On the other hand, the resistance due to the normal Hall effect (NHE), that is, the normal Hall resistance R _NHE , is proportional to the magnetic field orthogonal to the current.

The magnetic anisotropy evaluation device according to the embodiment of the present invention is a hole resistance measuring mechanism which is a mechanism for measuring the hole resistance of a thin film magnetic material having a flat flat surface, and a mechanism for applying a magnetic field to the magnetic material. The magnetic field application mechanism, the magnetic field application direction of the magnetic field to the plane, that is, the magnetic field angle control mechanism which is a mechanism capable of changing the magnetic field angle, and the magnetic field strength which is the applied strength of the magnetic field to the plane of the magnetic material are changed. It has a magnetic field strength control mechanism, which is a mechanism capable of performing the measurement, and a calculation mechanism, which is a mechanism for calculating the measured data. Further, it may have a magnetic field angle measuring mechanism which is a mechanism for measuring the magnetic field angle.

FIG. 1 is a block diagram showing a configuration of a magnetic anisotropy evaluation device 100 according to an embodiment of the present invention. The evaluation device of this embodiment includes a sample holder 1, a sample rod 9, an electromagnet 15, a DC power supply 13, a voltage measuring instrument 14, a controller 11, and an arithmetic unit 12. The arithmetic unit 12 is also referred to as an arithmetic mechanism. Of these, an element including the controller 11, the DC power supply 13, and the voltage measuring device 14 is referred to as a physical characteristic measuring device 10. The sample holder 1 can hold the sample (sample) 3. On the other hand, the sample holder 1 is attached to a sample rod 9 having a gear mechanism capable of changing the angle. Then, it is arranged in a pair of electromagnets 15 to which a magnetic field is applied. As a result, as the details will be described later, the sample rod 9 is rotated by a drive mechanism (not shown), and the applied angle of the magnetic field to the sample 3 held in the sample holder 1, that is, the magnetic field angle is relatively changed. Can be done. The physical characteristic measuring device 10 may include a mechanism for measuring an angle having a controller 11 which is a mechanism for measuring an angle, a DC power supply 13, and a voltage measuring device 14.

Further, the sample 3 is provided with a terminal for measuring the Hall resistance, and is electrically connected to the DC power supply 13 and the voltage measuring instrument 14 to which the DC current is applied. Further, the controller 11 is electrically connected to the electromagnet 15, the sample rod 9, the DC power supply 13, and the like, and controls the magnetic field application, the magnetic field strength, the magnetic field angle, and the Hall resistance measurement current. Further, the calculation mechanism 12 is electrically connected to the controller 11, the DC power supply 13, and the like, and executes the calculation for evaluating the magnetic anisotropy. The easy axis of magnetization of the magnetic thin film of sample 3 in FIG. 2 shows the case of being perpendicular to the surface of the magnetic thin film. However, even when the easy axis of magnetization of the magnetic thin film is tilted from the direction perpendicular to the surface of the magnetic thin film, the contents are the same as those described later.

FIG. 2 is a perspective view schematically showing a main part of the magnetic anisotropy evaluation device shown in FIG. Note that FIG. 2 shows an example in which the Hall sensor 2 is used as the magnetic field angle measuring mechanism. However, it is not limited to this. In FIG. 2, a part of the rod shape of the sample rod 9 is shown. As described above in FIG. 1, a sample holder 1 is attached to the sample rod 9. Then, the sample 3 is held by the sample holder 1. In the sample 3 of the present embodiment, the magnetic thin film to be measured is formed on a flat glass substrate or the like. A protective film made of a metal such as Au or Pt may be formed on the surface of the magnetic thin film. The film thickness of the magnetic thin film as sample 3 is preferably 1 to 100 nm. More preferably, the film thickness of the magnetic thin film is 2 to 20 nm. Further, the applied angle (magnetic field angle) θ _H of the magnetic field is an angle measured clockwise from the easy magnetization axis 4 perpendicular to the flat magnetic thin film surface.

In the sample holder 1, the hall sensor 2 is provided at a predetermined position at a predetermined distance along the longitudinal direction of the sample holder with respect to the position where the sample 3 is held. This makes it possible to measure the magnetic field angle when a magnetic field is applied to the sample 3. In the present embodiment, in order to measure the magnetic field angle of the sample 3, the Hall sensor 2 preferably has a plate-like shape like the sample 3. Further, it is preferable that the surface of the Hall sensor is substantially parallel to the surface of the magnetic thin film forming the sample 3. In the present specification, substantially parallel means that the angle between the surface of the Hall sensor and the surface of the magnetic thin film of the sample 3 is smaller than 0.5 degrees, preferably smaller than 0.2 degrees. Further, it is desirable that the Hall sensor 2 is arranged in the vicinity of the sample 3. In the present specification, the neighborhood is a range in which the magnetic field from the magnetic field application mechanism is applied at the same angle. Therefore, the Hall sensor 2 and the sample 3 are arranged on the same flat surface of one sample holder 1. Further, current terminals 7a and 7b and voltage terminals 8a and 8b are attached to the surface of the sample 3. This makes it possible to measure the Hall resistance of the sample 3. It is preferable to attach the terminals so that the direction of current flow and the direction of voltage measurement are orthogonal to each other as much as possible.

The Hall resistance measuring mechanism includes current terminals 7a and 7b attached to the surface of the magnetic thin film of sample 3, voltage terminals 8a and 8b, a DC power supply 13 for passing a DC current, and a voltage measuring device for measuring the DC voltage. 14 is configured. A magnetic field is applied to the sample 3, and a constant direct current I is passed from the direct current power supply 13 to the sample 3 via the current terminals 7a and 7b. Then, the voltage measuring instrument 14 measures the starting voltage V in the direction orthogonal to the DC current I of the sample 3 via the voltage terminals 8a and 8b. From these currents I and the measured voltage V, the Hall resistance R can be calculated as R = V / I.

In the present specification, the Hall resistance is an electromotive force generated in a direction orthogonal to the applied current I due to the Hall effect, and the voltage V due to the electromotive force is divided by the applied current I.

The magnetic field application mechanism includes an electromagnet 15 that generates a magnetic force and a DC power supply that supplies an electric current to the electromagnet. In FIG. 1, the controller 11 includes a DC power supply. The electromagnet 15 is preferable because the superconducting magnet can generate a strong magnetic force.

The magnetic field strength control mechanism has, in addition to the magnetic field application mechanism, a controller 11 for adjusting the amount of DC supplied to the electromagnet. In the evaluation of magnetic anisotropy according to the present invention, it is necessary to apply while controlling from a magnetic field of zero to a magnetic field of saturation magnetization or higher. Further, it is necessary to control and apply a magnetic field from zero magnetic field to a magnetic field having saturation magnetization or more in the opposite direction to the three surfaces of the sample.

The magnetic field angle control mechanism includes a sample rod 9 having a gear mechanism for rotating the sample holder 1 in the direction of the arrow shown in FIG. 1, and a controller 11 for controlling the rotation. The sample holder 1 may be rotated in the direction opposite to the direction of the arrow. For example, a rotating member connected to the gear is provided in the release window of the sample rod 9, and the sample holder 1 is mounted on the rotating member. By arranging such a sample rod 9 in an electromagnet 15 such as a superconducting magnet and controlling the rotation of the gear from the controller 11, the magnetic field angle with respect to the sample 3 can be arbitrarily changed. Although an example in which the sample rod 9 is provided with a rotation mechanism is shown here, a mechanism for rotating the sample rod 9 or a mechanism for rotating the electromagnet 15 may be used.

The calculation mechanism is inverting superposition for the magnetic field angle of Hall resistance, inverting superimposition for the magnetic field angle of Hall resistance, calculation of NHE component from the gradient depending on the magnetic field strength of inverting superposition, calculation of AHE component from zero section, and magnetization angle. Calculation of the magnetic field dependence of θ _M , calculation of the magnetic torque curve, curve fitting of the magnetic torque curve, calculation of the primary component Ku1 and secondary component Ku2 of magnetic anisotropy, and (all) magnetic anisotropy Ku Make a calculation.

Further, a mechanism for measuring the angle (magnetic field angle) of the applied magnetic field with respect to the sample 3 may be provided. The magnetic field angle measuring mechanism includes a mechanism for mechanically or optically reading the angle of the actual application mechanism or the angle of rotating the sample 3 with an encoder or the like. Further, as described above, the magnetic field angle may be measured using a Hall sensor. It is preferable to use a Hall sensor because the angle of the sample 3 at the position of the magnetic thin film can be accurately measured.

Next, the outline of the magnetic anisotropy evaluation process according to the present embodiment will be described. FIG. 3 is a flowchart showing this procedure.

First, in S01 of FIG. 3, the magnetic field angle-dependent curve of the Hall resistance R of the sample 3 is obtained as a magnetic material. As described above, the Hall resistance R (θ _H ) measured here includes various resistance components such as the normal Hall resistance R _NHE and the abnormal Hall resistance _RAHE .

Next, in S02, among these components, the magnetic field angle-dependent curves of the normal Hall resistance R _NHE , which is the NHE component of the Hall resistance R, and the abnormal Hall resistance R _AHE , which is the AHE component of the Hall resistance R, are obtained. That is, the magnetic field angle-dependent curve of the Hall resistance R is inverted and superposed with respect to the magnetic field angle. By doing so, the magnetic field angle-dependent curves of the normal Hall resistance R _NHE and the abnormal Hall resistance R _AHE are obtained.

Next, in S03, the magnetic field strength-dependent curve of the Hall resistance R of the magnetic material is obtained. The magnetic field angle θ _H = 0 °, that is, it is fixed perpendicular to the surface.

Further, in S04, the NHE component and the AHE component when the magnetic field angle θ _H = 0 are calculated. In the same manner as in S02, the magnetic field strength dependent curve of the Hall resistance R is inverted and superposed with respect to the magnetic field strength. By doing so, the normal hole resistance and the abnormal hole resistance at the magnetic field angle θ _H = 0 ° are obtained.

Next, in S05, the magnetization angle is obtained from the magnetic field angle-dependent curve of the normal Hall effect and the resistance due to the abnormal Hall effect obtained in S02, and the normal Hall resistance and the abnormal Hall resistance at the magnetic field angle θ _H = 0 ° obtained in S04. Find the magnetic field angle-dependent curve θ _M (θ _H ) of θ _M.

Next, in S06, the magnetic torque curve, that is, the magnetic field angle dependence of the magnetic torque is calculated from the magnetic field angle dependence curve of the magnetization angle obtained in S05.

The operations from S02 to S06 are also referred to as the first operation.

Finally, in S07, the magnetic anisotropy constant Ku is calculated from the magnetic torque curve obtained in S06.

In addition, S07 is also referred to as a second operation.

Hereinafter, each step of the above-mentioned magnetic anisotropy evaluation process will be described in detail.

S01 is a step of measuring the magnetic field angle-dependent curve of the Hall resistance R of the magnetic material. First, the sample 3 is prepared and mounted in a predetermined position of the sample holder 1. Further, current terminals 7a and 7b and voltage terminals 8a and 8b are attached to the surface of the sample 3. Then, the sample holder 1 is attached to the rotation mechanism portion of the sample rod 9. Further, the sample rod 9 is arranged in the electromagnet 15. After setting the sample as described above, the parameter α related to the magnetic angle is initialized. Further, a constant magnetic field is applied to the sample 3 by passing a predetermined current through the electromagnet 15. Here, the applied magnetic field strength is, for example, 3000 kA / m to 8000 kA / m. Then, the Hall resistance R is measured with a constant magnetic field strength applied. The Hall resistance is measured by the Hall resistance measuring mechanism as described above. Further, the Hall resistance R is measured by changing the magnetic field angle. Specifically, the magnetic field angle θ _H , which is the angle at which the magnetic field is applied, is set to α1, for example, in the present embodiment, the initial value is perpendicular to the upper surface of the sample 3, that is, 0 degree from the easy magnetization axis 4. , The Hall resistance R (θ _H ) at this magnetic field angle θ _H = α1 is measured. Then, the hole resistance R (θ _H ) at the magnetic field angle θ _H = α 2 is measured by changing the magnetic field angle to α 2 increased by a predetermined angle. While repeating this while increasing the predetermined angle, the magnetic field angle θ _H is changed from 0 degrees to 180 degrees, and the Hall resistance R (θ _H ) at which the magnetic field angle θ _H is from 0 degrees to 180 degrees is measured. .. By doing so, a magnetic field angle-dependent curve of the Hall resistance R is obtained. FIG. 4A shows an example of this magnetic field angle dependent curve.

On the other hand, the Hall resistance R obtained by this measurement can be expressed as being composed of the following components.

R = R ⁰ _NHE H cos θ _H + R ⁰ _AHE cos θ _M + R ⁰ _MR sin ² θ _M + R ⁰ _B equation (3)
here,
R ⁰ _NHE : NHE component obtained from the Hall resistance measured at θ _H = 0 R ⁰ _AHE : AHE component obtained from the Hall resistance measured at θ _H = 0 R ⁰ _MR : MR (magnetic resistance) component R ⁰ _B : Background resistance, which indicates resistance to the underlying layer or wiring.

θ _H : Magnetic field angle formed by the easily magnetized axis 4 and the magnetic field direction 6 θ _M : Angle formed by the easily magnetized axis 4 and the magnetization direction 5.

In S02, the MR component and the background resistance are removed from the measured value R (θ _H ) obtained in S01, and the magnetic field angle-dependent curve represented by the normal Hall resistance R _NHE and the abnormal Hall resistance _RAHE is calculated. Is.

That is, the MR component and the like are removed by inverting and superimposing the measured value R (θ _H ) of the Hall resistance with respect to the magnetic field angle θ _H. Specifically, it is removed by taking the difference between the measurement data R (θ _H ) when the magnetic field angle is θ _H and 180-θ _H. That is, (R (θ _H ) -R (180-θ _H )) / 2 is calculated, and as a result,
(R (θ _H ) -R (180-θ _H )) / 2 = R ⁰ _NHE H cos θ _H + R ⁰ _AHE cos θ _M equation (4)
Can be obtained. FIG. 4B shows an example of the magnetic field angle-dependent curves of the normal Hall resistance R _NHE and the abnormal Hall resistance _RAHE . Here, the MR component is eliminated because θ _M at the magnetic field angle θ _H and 180 − θ _H are equal due to the symmetry with respect to the magnetic field angle. This is because the background resistance does not depend on the magnetic field angle and is constant.

In S03, it is a step of measuring the magnetic field strength dependence curve of the Hall resistance R of the magnetic material. Similar to S01, first, the sample 3 is set in the electromagnet 15, and then a magnetic field is applied to the sample 3 by passing a predetermined current through the electromagnet 15. However, in S03, the magnetic field angle is fixed in the direction perpendicular to the upper surface of the sample 3, that is, θ _H = 0 °. Then, the magnetic field strength is changed, and the Hall resistance R at each magnetic field strength is measured. The Hall resistance is measured by the Hall resistance measuring mechanism as described above. For example, while changing the applied magnetic field strength from 0 kA / m → + 5600 kA / m → 0 kA / m → -5600 kA / m → 0 kA / m as a magnetic field in the opposite direction, the Hall resistance R is measured every 10 kA / m. do. By changing the applied magnetic field strength in this way, a curve that draws a hysteresis loop as shown in FIG. 5 can be obtained. The maximum value of the applied magnetic field strength does not have to be ± 5600 kA / m, but may be ± 3000 kA / m to ± 8000 kA / m. By doing so, a magnetic field strength dependent curve of the Hall resistance R is obtained.

S04 is a step of calculating the components of the normal Hall resistance R ⁰ _NHE and the abnormal Hall resistance R ⁰ _AHE when the magnetic field angle θ _H is 0 °.

Here, first, the magnetic field strength-dependent curve of the Hall resistance R obtained in S03 is inverted and superposed with respect to the magnetic field strength R (H) −R (—H). thus,
(R (H) -R (-H)) / 2 = R ⁰ _NHE H + R ⁰ _AHE formula (5)
To calculate. When θ _H = 0 °, the magnetization angle θ _M is 0 °, so cos θ _M is 1. FIG. 5 shows an example of a magnetic field strength dependent curve. At this time, as described above, the MR component and the background component are removed from the symmetry with respect to the magnetic field angle.

Here, in a portion where the magnetic field strength is larger than the saturated magnetic field of the magnetic material to be measured, for example, in the portion where the hysteresis loop is closed in FIG. 5, the AHE component does not change, but only the NHE component changes. Therefore, the Hall resistance change ΔR with respect to the magnetic field change amount ΔH becomes the normal Hall resistance R ⁰ _NHE . That is, ΔR / ΔH = R ⁰ _NHE in FIG.

Further, the place where the magnetic field strength is smaller than the saturated magnetic field of the magnetic material to be measured, for example, the part where the hysteresis loop is open in FIG. 5 is due to a constant AHE component and an NHE component proportional to the magnetic field strength H. .. Therefore, the anomalous Hall resistance R ⁰ _AHE is obtained as a magnetic field strength dependent zero intercept. That is, the abnormal hole resistance R ⁰ _AHE in FIG.

S05 is a step of calculating a magnetic field angle-dependent curve of the magnetization angle. Specifically, the normal Hall resistance R ⁰ _NHE and the abnormal Hall resistance R ⁰ _AHE obtained in S04 are substituted into the equation (4) which is the magnetic field angle-dependent curve of the resistance due to the normal Hall effect and the abnormal Hall effect obtained in S02. do.

First, the equation (4) is modified to obtain the following equation (6), and then the normal Hall resistance R ⁰ _NHE obtained in S04 is substituted. The curve thus obtained is shown in FIG. 4 (c).

R ⁰ _AHE cos θ _M = (R (θ _H ) -R (180-θ _H )) / 2-R ⁰ _NHE H cos θ _H equation (6)

Further, by dividing both sides by the abnormal hole resistance R ⁰ _AHE obtained in S04, normalization is performed so that the maximum value is 1. This is equal to the film plane vertical component of the normalized magnetization. By doing so, the magnetic field angle-dependent curve of the magnetization angle θ _M represented by the following equation (7) is calculated.

cosθ _M = ((R (θH) -R (180-θH)) / 2-R ⁰ _NHE H cosθ _H ) / R ⁰ _AHE equation (7)

S06 is a step of calculating the magnetic torque curve from the magnetic field angle-dependent curve of the magnetization angle θ _M obtained in S05. That is, by substituting the equation (7) obtained from cos θ _M obtained in S05 into the equation (2) of the magnetic torque described by the magnetization angle θ _M described above, the magnetic torque curve, that is, the magnetic field of the magnetic torque Get angle dependence. FIG. 4D shows an example of the magnetic field angle dependence of this torque.

T = HM _s sin (θ _H − θ _M ) Equation (2)
here,
θ _M = cos ^-1 (((R (θH) -R (180-θH)) / 2-R ⁰ _NHE Hcosθ _H ) / R ⁰ _AHE ) Equation (8)

_S07 is a step of calculating the magnetic anisotropy constant Ku from the magnetic torque curve obtained in S06. First, the 2θ _M and 4θ _M components of the magnetic torque curve are obtained by curve fitting. Next, the primary component K _u1 and the secondary component K _u2 of the magnetic anisotropy constant are calculated from the following magnetic anisotropy energy magnetic torque relational expression (Equation (9)).

T =-(K _u1 + K _u2 ) sin2θ _M + (K _u2 / 2) sin4θ _M equation (9)
Next, the total magnetic anisotropy constant _Ku is calculated by the relational expression (Equation (10)) of the magnetic anisotropy energy.

K _u = K _u1 + K _u2 + 2M _s ² formula (10)

Next, a modified example of the magnetic anisotropy evaluation method according to the present embodiment will be described.

In the steps S01 to S07, it is necessary to accurately evaluate the magnetic field angle θ _H. In particular, in the granular magnetic thin film, the normal Hall resistance component R ⁰ _NHE and the magnetic resistance component R ⁰ _MR have a large influence on the measured value of the Hall resistance. Therefore, in order to correctly derive the abnormal hole resistance component R ⁰ _AHE , it is necessary to improve the evaluation accuracy of θ _H. Therefore, in the modified example of the present embodiment, the magnetic anisotropy evaluation device uses the measured value obtained by the magnetic field angle measuring mechanism or the magnetic field angle measuring method as the magnetic field angle θ _H. As a result, the evaluation accuracy of the magnetic field angle θ _H is improved, while the set value at the time of evaluation is used, and as a result, the abnormal Hall resistance component R ⁰ _AHE can be derived more correctly, and the magnetic anisotropy K _u can be obtained. Can be evaluated more correctly.

In the magnetic anisotropy evaluation device in the modified example of the present embodiment, the Hall sensor 2 is used as the magnetic field angle measuring mechanism. The Hall sensor 2 measures the magnetic field strength in the natural direction. In this case, the magnetic field strength of the component in the direction perpendicular to the surface of the Hall sensor is measured. It can be measured from the Hall effect, which produces a Hall current in the direction perpendicular to the magnetic field and current. In the modification of the present embodiment, the step of correcting the deviation between the magnetic field measurement direction of the Hall sensor 2 and the easily magnetized axis 4 of the sample 3, the step of measuring the magnetic field strength of the Hall sensor 2, and the magnetic field angle θ _H are set. Includes the step of calculation. As a result, the direction of the easy magnetization axis 4 and the magnetic field strength θ _H of the sample 3 at the time of evaluation can be evaluated with high accuracy.

The specific method is shown below. The step of correcting the deviation between the magnetic field measurement direction of the Hall sensor 2 and the easily magnetized axis 4 of the sample 3 utilizes the fact that the maximum value is taken in the sample 3 at θ _H = 0 ° and therefore θ _M = 0 °. This is a step in which the magnetic field strength of the Hall sensor 2 at the time point is set to the magnetic field strength H _Z in the easy magnetization axis 4 direction. This makes it possible to adjust the origin of the θ _H dependence of the measured data during data analysis.

Next, in the step of measuring the magnetic field strength of the Hall sensor 2, the magnetic field strength H is also measured by the Hall sensor 2 at the same time as the measurement of the magnetic field angle dependence of the Hall resistance of the magnetic thin film of the sample 3. That is, the magnetic field angle dependence of the magnetic field strength H of the Hall sensor 2 is measured. This curve takes a cosine curve whose apex is a magnetic field angle θ _H of 0 °. Then, for example, the curve of the Hall resistance of the sample 3 with respect to the magnetic field strength H by the Hall sensor 2 can be obtained.

In the step of calculating the magnetic field angle θ _H , the magnetic field angle θ _H is calculated by the following formula from the magnetic field strength H read by the Hall sensor 2 and the magnetic field strength H _z in the easy magnetization axis 4 direction. By doing so, the magnetic field angle θ _H can be accurately obtained by using the magnetic field strength H read by the Hall sensor 2.

θ _H = cos ^-1 (H / H _z ) Equation (11)

The sample 3 is made of an insulator such as glass or an oxide crystal, and a magnetic thin film is formed on a substrate having a flat surface. The material that can be measured is not particularly limited as long as it is a material having magnetic anisotropy. Further, the magnetic material used for the measurement will be described in the case of a thin film having a predetermined thickness, but the present invention is not limited to this. It is also possible to measure in bulk molded into a predetermined shape. A protective film made of a metal such as Au or Pt may be formed on the surface of the magnetic thin film. The thickness of the substrate is preferably 0.2 to 10 mm. The thickness of the magnetic thin film is preferably 1 to 100 nm. More preferably, the film thickness is 1 to 20 nm. By doing so, the handling property of the magnetic thin film is good, and a value close to the characteristics of the original magnetic thin film and the characteristics of the magnetic thin film actually used as a magnetic recording medium can be obtained. For example, in a magnetic thin film made of an _L10 type ordered alloy, the characteristics of the original magnetic thin film may change depending on the film thickness. In particular, when the film thickness of the magnetic thin film is thicker than 20 nm, the regularity is disturbed, which is significantly different from the magnetic anisotropy constant used as a magnetic recording medium. Therefore, it is necessary to measure with a film thickness at which the characteristics of the original magnetic thin film can be obtained and a film thickness used as a magnetic recording medium.

However, in a magnetic thin film having such a thickness, the measurement output of the magnetic torque is small, and when an attempt is made to measure the magnetic anisotropy constant, the sample of the magnetic thin film formed on the substrate requires a large area. Therefore, it is difficult to accurately measure the magnetic anisotropy constant by the conventional method for measuring the mechanical magnetic torque due to the influence of the demagnetizing field from the substrate and the influence of the mechanical noise. For example, in the conventional measurement by mechanical magnetic torque, the RMS (root mean square) of the noise level is limited to 10 ^-5 Nm, and the measurement below that is not possible. It is difficult to accurately measure the magnetic anisotropy constant due to the influence of demagnetizing field and mechanical noise even with a thick film thickness, but especially when the magnetic thin film of the sample is as thin as 1 nm to 20 nm. Was difficult. The noise level is the level of the high frequency noise component existing in the signal component. Here, the level is shown by the RMS value. The noise level RMS is one of the indexes indicating the degree of noise.

On the other hand, in the magnetic anisotropy evaluation device and the magnetic anisotropy evaluation method of the present embodiment, since terminals are attached to the magnetic thin film and only the magnetic thin film is measured, there is almost no influence of the demagnetic field. Moreover, since the magnetic thin film can be measured electrically, mechanical noise can be reduced. Therefore, the accurate magnetic anisotropy constant can be measured even with the sample 3 having a film thickness as thin as 1 nm to 20 nm as described above. For example, in the measurement by the magnetic torque by the method of this embodiment, the noise level RMS could be reduced to 10 ^-9 Nm or less. Even if the film thickness of the magnetic thin film is 1 nm to 10 nm, it can be measured satisfactorily.

When the inventor actually evaluated the magnetic anisotropy of a magnetic thin film having a granular structure by a conventional method of directly measuring magnetic torque, the decrease in magnetic torque due to the granularization and the thick film of the magnetic thin film were performed. , And it has been confirmed that the magnetic anisotropy cannot be calculated correctly due to the limit of the measurement level. However, by using the magnetic anisotropy evaluation device and the magnetic anisotropy evaluation method of the present embodiment, the magnetic anisotropy is obtained. It is possible to calculate the sex correctly.

In the present embodiment, the arithmetic unit 12 is connected separately from the physical characteristic measuring device 10 to perform the calculation, but the arithmetic may be performed by providing a mechanism for calculating in the physical characteristic measuring device.

The magnetic anisotropy evaluation device of this embodiment includes a physical characteristic measuring device 10 (Physical Property Measurement System; PPMS) manufactured by Quantum Design, and a sample rod 9 for hole resistance measurement. The physical property measuring device 10 has at least an angle having a mechanism for applying a magnetic field to a magnetic material (sample holder 1, sample rod 9, and electromagnet 15), a controller 11, a DC power supply 13, and a voltage measuring instrument 14. It has a mechanism for measuring and is electrically connected to the arithmetic unit 12. The noise level RMS of this physical characteristic measuring device 10 was 10 ^-9 Nm or less. The sample rod 9 is a mechanism for uniaxially rotating the sample 3 for measurement so that the magnetic field angle θ _H between the magnetic field direction 6 applied by the physical property measuring device 10 and the easily magnetized axis 4 of the sample 3 for measurement can be changed. That is, it has a mechanism capable of changing the angle between the direction of the magnetic field and the easy axis of magnetization of the magnetic material. On the sample rod 9, a sample holder 1 in which a measurement terminal is arranged so as to measure the hole resistance of the sample 3 and read out the hole sensor 2 at the same time is arranged. The Hall resistance measurement of the sample 3 was performed by the four-terminal method in which the voltage terminals 8a and 8b and the current terminals 7a and 7b were arranged so that the magnetizing easy axis 4 of the magnetic material, the voltage direction, and the current direction were orthogonal to each other. .. This makes it possible to evaluate the abnormal Hall resistance proportional to the magnetization of the easy-to-magnetize axis 4. As the Hall sensor 2 of this embodiment, BHA-921 manufactured by FW Bell was used.

The magnetic material evaluated in this example is a magnetic material composed of FePt magnetic crystal grains of an _L10 type ordered alloy and a carbon (C) non-magnetic part surrounding the magnetic crystal grains on a glass substrate generally used as a magnetic recording medium. A thin film is formed with a film thickness of 4 nm. In this embodiment, the thickness of the magnetic thin film is 4 nm, but the magnetic thin film may be a continuous film, and the film thickness is preferably 1 nm or more, which is measurable, and more preferably 2 nm or more. Further, in the case of a magnetic thin film containing a regular alloy such as an _L10 type regular alloy, the thickness may be less than 10 nm in order to suppress a change in characteristics. 20% of carbon (C) in the non-magnetic portion is added at a volume fraction, whereby the FePt-C magnetic thin film has a granular structure. An underlayer containing MgO (magnesium oxide) is formed directly under the FePt-C magnetic thin film. For the measurement, a sample 3 cut into a rectangular parallelepiped having a plate thickness of 0.6 mm, a length of 3 mm, and a width of 8 mm was used.

In order to evaluate the magnetic anisotropy of the magnetic thin film, the same method as in the embodiment was used, the torque curve was calculated using the value of the Hall resistance of the magnetic thin film, and the magnetic anisotropy constant was calculated.

First, in S01 of FIG. 3, the magnetic field angle-dependent curve of the Hall resistance R of the magnetic material is measured. The magnetic field strength is constant. The Hall resistance R (θ _H ) measured here includes various resistance components in addition to the resistance due to the normal Hall resistance R _NHE and the abnormal Hall resistance _RAHE . The Hall resistance measurement of this example was performed with an applied magnetic field of 5600 kA / m and a current of 300 μA. Further, the magnetic field angle θ _H was changed from 0 to 180 degrees in 1 degree increments.

Next, in S02, among these components, the magnetic field angle-dependent curves of the normal Hall resistance R _NHE , which is the NHE component of the Hall resistance R, and the abnormal Hall resistance R _AHE , which is the AHE component of the Hall resistance R, are obtained. That is, the magnetic field angle-dependent curve of the Hall resistance R is inverted and superposed with respect to the magnetic field angle. By doing so, the magnetic field angle dependence curve by the normal Hall resistance R _NHE and the abnormal Hall resistance R _AHE is calculated.

Next, in S03, the magnetic field strength-dependent curve of the Hall resistance R of the magnetic material is measured. The magnetic field angle θ _H = 0 °, that is, it is fixed perpendicular to the surface.

Further, in S04, the NHE component and the AHE component when the magnetic field angle θ _H = 0 ° are calculated. The magnetic field strength dependent curve of the Hall resistance R is inverted and superposed with respect to the magnetic field strength. By doing so, the normal hole resistance and the abnormal hole resistance at the magnetic field angle θ _H = 0 ° are calculated.

Next, in S05, the magnetization angle is obtained from the magnetic field angle-dependent curve of the normal Hall effect and the resistance due to the abnormal Hall effect obtained in S02, and the normal Hall resistance and the abnormal Hall resistance at the magnetic field angle θ _H = 0 ° obtained in S04. Calculate the magnetic field angle dependence curve of.

Next, in S06, the magnetic torque curve, that is, the magnetic field angle dependence of the torque is calculated from the magnetic field angle dependence curve of the magnetization angle obtained in S05.

Finally, in S07, the magnetic anisotropy constant Ku is calculated from the magnetic torque curve obtained in S06.

By the steps S01 to S07, the formulas (1) to (10) described in the first embodiment can be obtained.

FIG. 4A shows the measurement data of the magnetic field angle dependence of the Hall resistance of the example. 4 (b) shows the data at S02 (formula (3)), FIG. 4 (c) shows the data at S05 (formula (5)), and FIG. 4 (d) shows the data after (S06). Equation (8)), that is, the magnetic torque curve is shown. Further, FIG. 5 shows the magnetic field strength dependence of the Hall resistance used in S05 (Equation (4). The normal Hall resistance R ⁰ _NHE has a magnetic field range of 4000 kA / m to 5600 kA / m and -5600 kA / m to -4000 kA / m. The magnetic torque curve at S06 has a sinusoidal shape as shown in FIG. 4 (d) and is theoretically easy to fit. The magnetism obtained as a result of this fitting. The anisotropy was K _u = 23.6 Merg / cm ³ , which was a reasonable value for the magnetic thin film of this example, and the sum of residual squares in the fitting was 0.023 (Merg / cm). ³ ) It was ² / deg., And it was found that the fitting could be performed without any problem. The sum of residual squares is the sum of the squares of the numerical differences between the data curve and the fitting curve, and is the sum of the fittings. It is a scale for evaluating discrepancies. In a sample with magnetic anisotropy K _u = 10 to 70 Merg / cm ³ , the residual sum of squares should be 1.0 (Merg / cm ³ ) ² / deg. More preferably, the sum of residual squares is (Merg / cm ³ ) ² / deg. Is 0.1 or less.

In this embodiment, the magnetic field angle θ _H is changed from the set value of 0 to 180 degrees in increments of 1 degree, but for example, the magnetic torque curve may be changed in increments of even numbers to the extent that a magnetic torque curve can be obtained. The angle tick may be changed at random.

This embodiment is the same as that of the embodiment except that the magnetic field angle is not the measured value by the Hall sensor but the set value of the apparatus.

FIG. 6A shows the measurement data of the comparative example. 6 (b) shows the data at S02 (formula (3)), FIG. 6 (c) shows the data at S05 (formula (5)), and FIG. 6 (d) shows the data at S06 (formula (formula (c)). 8) Magnetic torque curve) is shown. As shown in FIG. 6D, the waveform is slightly disturbed from the sine wave waveform that should be theoretically obtained, but accurate fitting with the theoretical formula was possible. The sum of squared residuals when fitting is performed is 0.505 (Merg / cm ³ ) ² / deg. The fitting accuracy was slightly inferior to that of the examples, but there was no problem in the measurement. It turned out that the fitting accuracy was poor. It is considered that this is because the measurement accuracy of the magnetic field angle is slightly better when the magnetic field angle is measured by the Hall sensor than when the set value of the device is used as in this experimental example.

Comparative example

In this comparative example, the magnetic torque curve was measured mechanically. A torque magnetometer manufactured by Hayama Co., Ltd. was used for the measurement. The same sample as in the examples was used as the magnetic material used for the measurement.

FIG. 7 shows a magnetic torque curve. As shown in FIG. 7, positive torque from 0 to 22 degrees, negative torque from 22 degrees to 90 degrees, positive torque from 90 degrees to 157 degrees, negative torque from 157 degrees to 180 degrees. It became the torque of. In addition, there were many high-frequency components due to noise. Therefore, a large error occurs in the curve fitting according to the equation (9). The noise level RMS was about ^10-5 Nm. The residual sum of squares by curve fitting is 3.05 (Merg / cm ³ ) ² / deg. It was found that the fitting accuracy was significantly worse than that of the examples. Therefore, the measured value of Ku fluctuates greatly for each measurement, and accurate measurement is difficult.

From the above, it can be seen that according to the present invention, good measurement can be performed even if the magnetic thin film is as thin as about 10 nm.

1 Sample holder 2 Hall sensor 3 Sample 4 Magnetization easy axis 5 Magnetization direction 6 Magnetic field direction 7a, 7b Current terminal 8a, 8b Voltage terminal 9 Sample rod 10 Physical characteristic measuring device 11 Controller 12 Computing device 13 DC power supply 14 Voltage measuring device 15 Electromagnet 100 Magnetic anisotropy evaluation device

Claims (31)

A mechanism for measuring the Hall resistance of a magnetic material of a thin film having a flat flat surface,
A mechanism for applying a magnetic field to the magnetic material and
The first calculation for calculating the magnetic torque curve from the application magnetic field angle dependence of the Hall resistance of the magnetic material, and
A second calculation mechanism for calculating the magnetic anisotropy constant from the calculated magnetic torque curve, and
A magnetic anisotropy evaluation device characterized by being equipped with. In the first calculation, the magnetic field angle dependence of the magnetization angle is calculated based on the applied magnetic field angle dependence of the Hall resistance of the magnetic material, and the magnetic torque curve is calculated from the magnetic field angle dependence of the magnetization angle. The magnetic anisotropy evaluation apparatus according to claim 1. A mechanism capable of changing the magnetic field angle, which is the direction in which the magnetic field is applied with respect to the plane of the magnetic material,
A mechanism capable of changing the magnetic field strength, which is the applied strength of the magnetic field on the plane of the magnetic material,
Further prepare
The applied magnetic field of the Hall resistance is based on the Hall resistance measured by the measuring mechanism when the magnetic field is applied to the magnetic material by the mechanism for applying the magnetic field while changing the magnetic field angle by the mechanism for changing the magnetic field angle. Find the angle dependence,
The applied magnetic field of the Hall resistance obtained based on the Hall resistance measured by the measuring mechanism when the magnetic field is applied to the magnetic material by the mechanism for applying the magnetic field while changing the magnetic field strength by the mechanism for changing the magnetic field strength. The magnetic anisotropy evaluation device according to claim 2, wherein the magnetic field angle dependence of the magnetization angle is obtained based on the strength dependence and the applied magnetic field angle dependence of the Hall resistance. The mechanism for measuring the Hall resistance includes a current terminal and a voltage terminal attached to the surface of the magnetic material, a DC power supply electrically connected to the current terminal, and a voltmeter electrically connected to the voltage terminal. The magnetic anisotropy evaluation device according to any one of claims 1 to 3, wherein the magnetic anisotropy evaluation device is provided. The magnetic anisotropy evaluation device according to any one of claims 1 to 4, further comprising a mechanism for measuring a magnetic field angle formed by a plane of the magnetic material and an application direction of the magnetic field. The mechanism for measuring the magnetic field angle is
A Hall sensor arranged in the vicinity of the magnetic material and substantially on the same plane as the plane of the magnetic material.
A DC power supply that is electrically connected to the current terminal of the Hall sensor,
The magnetic anisotropy evaluation device according to claim 5, further comprising a voltage measuring device that is electrically connected to the voltage terminal of the Hall sensor. The magnetic anisotropy evaluation device according to claim 6, further comprising an angle measuring mechanism for reading the magnetic field with the Hall sensor and measuring the applied direction of the magnetic field from the comparison between the applied magnetic field strength and the reading magnetic field strength. By analyzing the dependence of the electric resistance of the magnetic material on the applied magnetic field angle and utilizing the fact that the applied magnetic field angle at which the electric resistance reaches the maximum value coincides with the easy axis of magnetization, the magnetic field measurement direction of the Hall sensor and the magnetic material The magnetic anisotropy evaluation device according to claim 7, further comprising a mechanism for correcting the deviation of the easy axis of magnetization.
In the first calculation, the applied magnetic field angle-dependent curve of the Hall resistance of the magnetic material is obtained.
The magnetic anisotropy evaluation device according to any one of claims 1 to 7, wherein the operation is to invert the angles, superimpose them, and substitute the normal hole resistance component and the abnormal hole resistance component. The normal Hall resistance component and the abnormal Hall resistance component are characterized in that the magnetic field strength dependent curve of the Hall resistance is inverted and superposed with the magnetic field angle set to 0 °, and is calculated by the inverted superimposition curve. The magnetic anisotropy evaluation device according to claim 9. A voltage measuring instrument that measures the Hall resistance with respect to the magnetic field angle θ _H from 0 ° to 180 ° and sets θ _H = 0 ° to measure the magnetic field strength dependence of the Hall resistance.
Using the applied magnetic field angle dependence of the anisotropy hole resistance component, the angle θ _M formed by the easy axis of magnetization and the magnetization direction is obtained, and the calculated mechanism for obtaining the magnetic torque curve using the angle θ _M. The magnetic anisotropy evaluation device according to claim 8. The magnetic field angle-dependent curve of the Hall resistance of the magnetic material is a normal Hall resistance component and an abnormal Hall resistance component obtained from the Hall resistance measured at R (θ _H ) and θ _H = 0 as the measured value of the Hall resistance. It is expressed by the following equation (a) using R ⁰ _NHE , R ⁰ _AHE , and the applied magnetic field H of the magnetic field, respectively.
(R (θ _H ) -R (180-θ _H )) / 2 = R ⁰ _NHE H cos θ _H + R ⁰ _AHE cos θ _M equation (a)
The magnetic field strength dependence of the magnetization angle is expressed by the following (formula (b)).
(R (θ _H ) -R (180-θ _H )) / 2 = R ⁰ _NHE H + R ⁰ _AHE cos θ _M equation (b)
The magnetic torque curve T is expressed by the following equation (c), where Ms is the spontaneous magnetization.
T = HM _s sin (θ _H − θ _M ) Equation (c)
The magnetic anisotropy evaluation device according to claim 11, wherein the magnetic anisotropy is evaluated. In the second calculation, the magnetic torque curve is fitted with the sin2θ component and the sin4θ component.
Derivation of the primary component and the secondary component of the magnetic anisotropy constant,
The magnetic anisotropy evaluation device according to claim 1, wherein the operation is to calculate the magnetic anisotropy constant. K _u1 which is the primary component and K _u2 which is the secondary component are calculated from the following formula (d).
T =-(K _u1 + K _u2 ) sin2θ _M + (K _u2 / 2) sin4θ _M equation (d)
The magnetic anisotropy evaluation device according to claim 13, wherein the magnetic anisotropy constant _Ku is calculated from the following equation (e).
K _u = K _u1 + K _u2 + 2M _s ² formula (e) The magnetic anisotropy evaluation device according to any one of claims 1 to 14, wherein the magnetic material has a film thickness of 1 nm or more and less than 20 nm. The step of measuring the Hall resistance of a magnetic material of a thin film having a flat flat surface,
The step of applying a magnetic field to the magnetic material and
A step of calculating the magnetic torque curve from the application magnetic field angle dependence of the Hall resistance of the magnetic material, and a step of calculating the magnetic anisotropy constant from the calculated magnetic torque curve.
A magnetic anisotropy evaluation method characterized by being provided with. In the calculation of the magnetic torque curve, the magnetic field angle dependence of the magnetization angle is calculated based on the applied magnetic field angle dependence of the Hall resistance of the magnetic material, and the torque curve is calculated from the magnetic field angle dependence of the magnetization angle. The magnetic anisotropy evaluation method according to claim 16. A means capable of changing the magnetic field angle, which is the direction in which the magnetic field is applied with respect to the plane of the magnetic material,
A means capable of changing the magnetic field strength, which is the applied strength of the magnetic field with respect to the plane of the magnetic material,
Further prepare
The applied magnetic field of the Hall resistance is based on the Hall resistance measured by the measuring mechanism when the magnetic field is applied to the magnetic material by the mechanism for applying the magnetic field while changing the magnetic field angle by the mechanism for changing the magnetic field angle. Find the angle dependence,
The applied magnetic field of the Hall resistance obtained based on the Hall resistance measured by the measuring mechanism when the magnetic field is applied to the magnetic material by the mechanism for applying the magnetic field while changing the magnetic field strength by the mechanism for changing the magnetic field strength. The magnetic anisotropy evaluation method according to claim 17, wherein the magnetic field angle dependence of the magnetization angle is obtained based on the strength dependence and the applied magnetic field angle dependence of the Hall resistance. The Hall resistance is measured by a current terminal and a voltage terminal attached to the surface of the magnetic material, a DC power supply electrically connected to the current terminal, and a voltage measuring instrument electrically connected to the voltage terminal. The magnetic anisotropy evaluation method according to any one of claims 16 to 18, wherein the magnetic anisotropy is evaluated. The measurement of the magnetic field angle-dependent curve of the Hall resistance of the magnetic material is performed by electrically connecting a Hall sensor arranged substantially on the same plane as the plane of the magnetic material in the vicinity of the magnetic material and the current terminal of the Hall sensor. The magnetic anisotropy evaluation method according to claim 16, wherein the method is performed by a DC power supply and a voltage measuring device electrically connected to the voltage terminal of the Hall sensor. 16. to claim 16, wherein in the step of calculating the magnetic anisotropy constant from the magnetic torque curve, fitting based on the magnetic torque curve is used as a means for evaluating the magnetic anisotropy of the magnetic material. The magnetic anisotropy evaluation method according to any one of 20. In the step of measuring the magnetic field angle-dependent curve of the Hall resistance of the magnetic material, the magnetic field applied from the mechanism for applying the magnetic field is read by the Hall sensor, and the application direction of the magnetic field is determined from the comparison between the applied magnetic field strength and the read magnetic field strength. The magnetic anisotropy evaluation method according to claim 21, further comprising an angle measuring method for measuring. In the step of measuring the magnetic field angle dependence curve of the Hall resistance of the magnetic material, the magnetic field angle dependence of the electric resistance of the magnetic material is analyzed, and the deviation between the magnetic field measurement direction of the Hall sensor and the easy axis of magnetization of the magnetic material is determined. The magnetic anisotropy evaluation method according to claim 22, wherein the correction is performed. The calculation of the magnetic torque curve is performed by using the applied magnetic field angle dependence curve of the Hall resistance of the magnetic material.
The magnetic anisotropy evaluation method according to any one of claims 16 to 23, wherein the operation is to invert the angles, superimpose them, and substitute the normal hole resistance component and the abnormal hole resistance component. The normal Hall resistance component and the abnormal Hall resistance component are calculated by inverting the magnetic field strength and superimposing the magnetic field strength dependence curve of the Hall resistance with the magnetic field angle set to 0 °. The magnetic anisotropy evaluation method according to claim 24. When measuring the applied magnetic field angle dependent curve, measure the Hall resistance with respect to the magnetic field angle θ _H from 0 ° to 180 °.
When calculating the normal Hall resistance component and the abnormal Hall resistance component, set θ _H = 0 ° and measure the magnetic field strength dependence of the Hall resistance.
When calculating the applied magnetic field angle dependence curve, the angle θ _M between the easy axis of magnetization and the magnetization direction is obtained by using the application magnetic field angle dependence of the abnormal Hall resistance component.
The magnetic anisotropy evaluation method according to claim 23, wherein the magnetic torque curve is obtained by using the angle θ _M when calculating the magnetic torque curve. The magnetic field angle-dependent curve of the Hall resistance includes the normal Hall resistance component and the abnormal Hall resistance component obtained from the Hall resistance measured at R (θ _H ) and θ _H = 0, respectively. It is expressed by the following equation (a) using R ⁰ _NHE , R ⁰ _AHE , and the applied strength H of the magnetic field.
(R (θ _H ) -R (180-θ _H )) / 2 = R ⁰ _NHE H cos θ _H + R ⁰ _AHE cos θ _M equation (a)
The magnetic field strength dependence of the magnetization angle is expressed by the following (formula (b)).
(R (θ _H ) -R (180-θ _H )) / 2 = R ⁰ _NHE H + R ⁰ _AHE cos θ _M equation (b)
The magnetic torque curve T is expressed by the following equation (c), where Ms is the spontaneous magnetization.
T = HM _s sin (θ _H − θ _M ) Equation (c)
The magnetic anisotropy evaluation method according to claim 26. The calculation of the magnetic anisotropy constant is performed by fitting the magnetic torque curve with the sin2θ component and the sin4θ component.
Derivation of the primary component and the secondary component of the magnetic anisotropy constant,
The magnetic anisotropy evaluation method according to any one of claims 16 to 27, which is an operation for calculating the magnetic anisotropy constant. K _u1 which is the primary component and K _u2 which is the secondary component are calculated from the following formula (d).
T =-(K _u1 + K _u2 ) sin2θ _M + (K _u2 / 2) sin4θ _M equation (d)
The magnetic anisotropy evaluation method according to claim 28, wherein Ku, which is the magnetic _anisotropy constant, is calculated from the following equation (e).
K _u = K _u1 + K _u2 + 2M _s ² formula (e) The magnetic anisotropy evaluation method according to any one of claims 16 to 29, wherein the film thickness of the magnetic material to be measured is 1 nm or more and less than 20 nm. In order to evaluate the magnetic anisotropy of a magnetic material, a magnetic torque curve is calculated using the applied magnetic field angle dependence of the Hall resistance of the magnetic material, and a magnetic anisotropy constant is calculated from the magnetic torque curve. mechanism.

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