JP5469590B2 - Magneto-optical spectrum spectrometer, magneto-optical spectrum measuring method and program - Google Patents

Description

  The present invention relates to magneto-optical spectroscopy, and more particularly to a magneto-optical spectrum measurement technique.

  In general, light is a wave in which an electric field and a magnetic field vibrate. Light that vibrates with an electric field and a magnetic field aligned in one direction is called linearly polarized light, and the vibration direction of the electric field is called a polarization plane. When a material present in a magnetic field is irradiated with linearly polarized light, the plane of polarization of the light rotates due to the optical rotation of the material. This is called a magneto-optical effect. The magneto-optic effect has been applied to magneto-optical disks and optical switches, and research on various materials has been advanced. In addition, due to recent rapid advances in spintronics research, establishment of methods for observing magneto-optical spectra of magnetic materials at high speed, high accuracy, and low cost is required.

  As a method for measuring the magneto-optical effect, for example, a rotating polarizer method and a polarization modulation method are known (see Patent Document 1). The rotating polarizer method and the polarization modulation method have the following advantages and disadvantages. The rotational polarizer method can determine the absolute value of an observed magneto-optical signal (hereinafter referred to as an MO signal), but takes a long time to measure. On the other hand, the polarization modulation method can efficiently measure the MO spectrum, but cannot determine the absolute value of the MO signal. So far, the wavelength dependence of the magneto-optic effect, so-called magneto-optic spectrum, has been observed mainly by the polarization modulation method. This measuring method using the polarization modulation method has already been described in detail in Non-Patent Document 1, and measuring devices are also commercially available.

JP 2004-294293 A

Katsuaki Sato, “Light and Magnetism”, Asakura Publishing, November 20, 2001, p.90-115

  Conventionally, a commercially available measuring apparatus using a polarization modulation method for measuring the MO spectrum is calibrated in advance in a factory before being shipped as a product, so that the absolute value of the MO signal can be directly determined at the measurement site. Has been. In other words, this conventional measuring apparatus calibrates the measurement result obtained at the measurement site using the parameters calibrated once at the factory to obtain the absolute value of the MO signal. However, the calibration conditions may change due to on-site experimental conditions and changes in the characteristics of the photoelastic modulator. Therefore, it is ideal to perform calibration on site for each measurement according to the calibration conditions, and in the research field using a magneto-optical spectrometer, it is desired to re-calibrate the magneto-optical spectrometer for each measurement. Yes. However, since the conventional measuring device cannot be calibrated every time it is measured, there is a doubt about the reliability of the data.

  The MO signal observed in the reflected light of the sample is, in principle, the linear sum of the polar Kerr effect, the longitudinal Kerr effect, and the linear dichroism, but in many studies, the signal observed from the reflected light. Is governed by the polar Kerr effect. For this reason, a commercially available polar Kerr effect measurement device using the polarization modulation method is configured on the assumption that the magneto-optical effect is caused only by the polar Kerr effect, and incident light is irradiated obliquely to the sample surface. Is not always correct. In many measuring apparatuses, since the sample is irradiated with light obliquely, the observed data may contain an error.

  In view of this, a method of combining both of the rotating polarizer method and the polarization modulation method with a focus on mutually complementing advantages and disadvantages is conceivable. That is, if the MO spectrum is observed by the polarization modulation method and then the MO signal is calibrated by the rotating polarizer method, a correct MO spectrum can be obtained. However, since the measuring device using the rotating polarizer method is different from the measuring device using the polarization modulation method, it takes time and effort to measure.

The present invention has been made in view of the above problems, and provides a magneto-optical spectrum spectrometer, a magneto-optical spectrum measuring method, and a program capable of calibrating the absolute value of a signal observed as a magneto-optical effect. Is an issue.
Another object of the present invention is to provide a magneto-optical spectrum spectrometer, a magneto-optical spectrum measurement method, and a program that can efficiently measure a signal observed as a magneto-optical effect.

In order to solve the above-mentioned problems, the inventors of the present application have made various studies on measuring devices and measuring methods of the rotating polarizer method and the polarization modulation method. The difference between these measuring devices is the angle of the polarizing plate installed in the optical measurement system and the presence or absence of a photoelastic modulator. It has been found that it is possible to realize computer control of on / off of the modulation function of the modulator with a single measuring device. In addition, it has been found that the measurement efficiency can be drastically improved by realizing the rotating polarizer method and the polarization modulation method with one measuring device in the following procedures (A1) to (A3). It was.
(A1) The absolute value of the MO signal is determined using the rotating polarizer method.
(A2) Using the rotating polarizer method, the change of the MO signal with respect to the incident light polarization plane is observed, and the origin of the MO signal is determined from its behavior.
(A3) An MO spectrum is observed using a polarization modulation method.

  Therefore, the magneto-optical spectrum spectroscope according to claim 1 of the present invention includes a light source, a spectroscope, and a first straight line arranged as a measurement system using a polarization modulation method for measuring a spectrum of the magneto-optical characteristic of a sample. A polarizing plate, a photoelastic modulator, a magnetic field applying unit, a second linear polarizing plate, a light detecting unit, a voltmeter, a lock-in amplifier, and a wavelength of light of a predetermined wavelength that is split by the spectrometer. Control means for controlling the operation including switching at a preset timing, storage means for storing voltage values respectively measured by the voltmeter and the lock-in amplifier, and the sample based on the stored voltage values And a calculating means for calculating a Kerr rotation angle as a magneto-optical characteristic of the linear optical polarizer, wherein each linearly polarizing plate has a predetermined polarization plane angle by rotation. A linear polarizing plate with a rotation mechanism that can be adjusted so that the control means includes a first measurement control means and a second measurement control means, and the calculation means includes a first calculation means and a correlation determination. Means, second calculation means, and third calculation means. The arrangement of the measurement system using the polarization modulation method is known.

  According to such a configuration, in the magneto-optical spectrum spectrometer, the control unit turns off the polarization modulation function of the photoelastic modulator and sets the angle of the polarization plane in each linearly polarizing plate by the first measurement control unit. Control is performed to measure the voltage value detected by the voltmeter using the rotating polarizer method to be changed, and each measured value for each angle of the polarization plane is recorded in the storage means. Then, the second measurement control means turns on the polarization modulation function of the photoelastic modulator, fixes each linearly polarizing plate at a predetermined angle, and changes the wavelength of light dispersed by the spectrometer. Control is performed to measure voltage values detected by the voltmeter and the lock-in amplifier using a polarization modulation method, and the measured values are recorded in the storage means. Then, in the magneto-optical spectrum spectrometer, the calculation means is a first calculation means for each measurement value for each angle of polarization plane in each linearly polarizing plate using the rotating polarizer method stored in the storage means. On the basis of the absolute value of the Kerr rotation angle at the predetermined wavelength. Then, the computing means discriminates whether or not there is a correlation between the absolute value of the Kerr rotation angle at the predetermined wavelength and the angle of the incident light polarization plane which is the polarization plane in the first linearly polarizing plate.

  Here, the polar Kerr effect, which is one of the magneto-optical effects, has no correlation because it does not depend on the angle of the plane of polarization of incident light. However, the correlation between the longitudinal Kerr effect and linear dichroism depends on both. is there. Therefore, in the magneto-optical spectrum spectrometer, when it is determined that there is no correlation between the absolute value of the Kerr rotation angle and the angle of the incident light polarization plane, the observed magneto-optical effect is caused by the polar Kerr effect. The calculation means calculates the spectrum of the Kerr rotation angle of the sample based on the measurement value using the polarization modulation method stored in the storage means by the second calculation means. Then, the calculation means uses the third calculation means to convert the Kerr rotation angle value in the spectrum calculated by the second calculation means to the converted value that matches the absolute value of the Kerr rotation angle calculated by the first calculation means. And the calculated Kerr rotation angle spectrum is calculated as the spectrum of the magneto-optical characteristic of the sample.

  The magneto-optical spectrum spectrometer according to claim 2 is the magneto-optical spectrum spectrometer according to claim 1, wherein the magnetic field applying means applies a magnetic field in a direction perpendicular to the surface of the sample. And an in-plane magnetic field applying means for applying a magnetic field in the in-plane direction of the sample, and the correlation determining means of the computing means is configured to rotate the Kerr rotation angle when a magnetic field is applied in a direction perpendicular to the surface of the sample. Is calculated using a measured value when a magnetic field is applied in the in-plane direction of the sample and parallel to the light incident surface. If there is a correlation between the absolute value of the Kerr rotation angle and the angle of the incident light polarization plane, and there is a correlation between them, the magneto-optical effect of the sample is a longitudinal Kerr effect or a linear two-color effect. It is preferable to determine that a gender contribution is included. Arbitrariness.

  According to such a configuration, the magneto-optical spectrum spectrometer is configured to calculate the absolute value of the Kerr rotation angle calculated from the measurement value when a magnetic field is applied to the sample in the direction perpendicular to the surface and the angle of the incident light polarization plane in the measurement. If it is determined that there is a correlation, the presence or absence of the correlation can be similarly examined based on the measured value when the magnetic field is applied to the sample in the in-plane direction. Here, it is known that the longitudinal Kerr effect is such that the traveling vector of light applied to the sample is proportional to the inner product of the projection vector and the magnetization vector in the in-plane direction. If the rotation angle of polarized light measured while applying a magnetic field in the direction perpendicular to the surface of the sample and controlling the direction of magnetization of the sample depends on the angle of the incident light polarization surface in the measurement, It is thought to be due to the magneto-optical effect. Therefore, according to the magneto-optical spectrum spectrometer, the presence or absence of correlation is examined based on the measured value while controlling the magnetization direction of the sample in an arrangement in which the longitudinal Kerr effect appears in principle. It can be determined that the Kerr rotation angle is not due to the polar Kerr effect but to the vertical Kerr effect or linear dichroism. Therefore, even when the spectrum due to the polar Kerr effect cannot be obtained by the magneto-optical signal observed from the sample, the magneto-optical effect observed in the target sample may be due to the longitudinal Kerr effect or linear dichroism. As can be seen, it is possible to obtain a spectrum due to vertical Kerr effect or linear dichroism by some means.

  The magneto-optical spectrum spectrometer according to claim 3 is the magneto-optical spectrum spectrometer according to claim 2, wherein the correlation determining means of the computing means is in an in-plane direction of the sample and incident light. If there is a correlation between the absolute value of the Kerr rotation angle calculated using the measured value when a magnetic field is applied parallel to the surface and the angle of the incident light polarization plane, the in-plane direction of the sample Further, it is further determined whether or not there is a correlation between the absolute value of the Kerr rotation angle calculated using the measured value when the magnetic field is applied in the normal direction of the light incident surface and the angle of the incident light polarization surface. If there is a correlation between them, the determination that the contribution of the vertical Kerr effect is included is reversed, and it is determined that the magneto-optic effect of the sample includes a contribution of linear dichroism. preferable.

  According to such a configuration, when the magneto-optical spectrum spectrometer determines that there is a correlation based on the measured value while controlling the magnetization direction of the sample in an arrangement in which the longitudinal Kerr effect appears in principle, Based on the measured value when a magnetic field is applied in the in-plane direction of the sample and in the normal direction of the light incident surface, the presence or absence of correlation can be similarly examined. Here, it is known that the linear dichroism is proportional to the relative relationship between the magnitude of the in-plane magnetization of the magnetization and the angle of the incident light polarization plane. Further, when it is estimated that the signal obtained in the arrangement of the applied magnetic field in which the vertical Kerr effect appears in principle is caused by the vertical Kerr effect or linear dichroism, the vertical Kerr effect does not appear in principle. In principle, if the absolute value of the Kerr rotation angle still depends on the angle of the polarization plane of the incident light even in the signal measured while controlling the magnetization direction of the sample by applying a magnetic field in such an arrangement, in principle However, it can be said that the Kerr rotation angle at this time is not caused by the vertical Kerr effect, and it is considered that the Kerr rotation angle is caused by linear dichroism as the remaining possibility. Therefore, according to the magneto-optical spectrum spectrometer, it can be determined that the Kerr rotation angle is caused by linear dichroism. Therefore, even if the spectrum due to the polar Kerr effect cannot be obtained by the magneto-optical signal observed from the sample, it can be seen that the magneto-optical effect observed in the target sample is due to linear dichroism, Thus, it is possible to obtain a spectrum caused by linear dichroism.

  In order to solve the above problem, a magneto-optical spectrum measurement method according to claim 4 of the present invention includes a light source arranged as a measurement system using a polarization modulation method for measuring a spectrum of a magneto-optical characteristic of a sample, A spectroscope, a first linearly polarizing plate, a photoelastic modulator, a magnetic field applying unit, a second linearly polarizing plate, a light detecting unit, a voltmeter, a lock-in amplifier, a control unit, and a storage unit A magneto-optical spectrum measuring method in a magneto-optical spectrum spectroscopic device comprising a computing means, wherein each linearly polarizing plate is a linearly polarized light with a rotation mechanism that can be adjusted so that the angle of the polarization plane becomes a predetermined value by rotation. A board, including a first measurement control step, a first calculation step, a correlation determination step, a second measurement control step, a second calculation step, and a third calculation step; It was.

  According to this procedure, in the magneto-optical spectrum measurement method, in the first measurement control step, the polarization modulation function of the photoelastic modulator is turned off by the control means, and the polarization plane of each linearly polarizing plate is changed. Control for measuring the voltage value detected by the voltmeter is performed using a rotating polarizer method that changes the angle of each of the angles, and the measured values for each angle of the polarization plane are recorded in the storage means. In the measurement using this rotating polarizer method, at least one wavelength may be used. Then, in the first calculation step, the predetermined value is calculated by the calculating means based on the measured values for the respective polarization plane angles of the linear polarizing plates using the rotating polarizer method stored in the storage means. The absolute value of the Kerr rotation angle at the wavelength is calculated. In the correlation determination step, the calculation means determines whether or not there is a correlation between the absolute value of the Kerr rotation angle at the predetermined wavelength and the angle of the incident light polarization plane that is the polarization plane of the first linearly polarizing plate. . Here, when it is determined that there is no correlation between the absolute value of the Kerr rotation angle and the angle of the incident light polarization plane, in the second measurement control step, the polarization modulation of the photoelastic modulator is performed by the control means. Detected by the voltmeter and the lock-in amplifier using a polarization modulation method in which the function is turned on and each linearly polarizing plate is fixed at a predetermined angle and the wavelength of light split by the spectrometer is changed. Control for measuring the voltage value to be performed is performed, and each measured value is recorded in the storage means. In the second calculation step, the calculation means calculates a spectrum of the Kerr rotation angle of the sample based on the measurement value using the polarization modulation method stored in the storage means. Further, in the third calculation step, the value of the Kerr rotation angle in the spectrum calculated in the second calculation step is adapted to the absolute value of the Kerr rotation angle calculated in the first calculation step by the calculation means. The conversion value to be obtained is obtained, and the Kerr rotation angle value in the spectrum is multiplied by the conversion value to calculate the corrected Kerr rotation angle spectrum as the spectrum of the magneto-optical characteristics of the sample.

As a result, in the magneto-optical spectrum measurement method, the correlation determination step determines that there is no correlation between the absolute value of the Kerr rotation angle at a predetermined wavelength and the angle of the incident light polarization plane. Measurement using the polarization modulation method can be performed after determining that the rotation angle is caused by the polar Kerr effect. Therefore, according to the magneto-optical spectrum measurement method, the spectrum of the calibrated magneto-optical characteristic can be measured as the spectrum of the Kerr rotation angle caused by the polar Kerr effect of the sample.
In the magneto-optical spectrum measurement method, the Kerr rotation angle measured accurately by the rotating polarizer method is compared with the Kerr rotation angle spectrum measured by the polarization modulation method in a relatively short time in the third calculation step. Since the spectrum of the Kerr rotation angle is calibrated simply by performing the operation of uniformly multiplying the converted value using the absolute value, the calibrated spectrum of the magneto-optical characteristic can be measured in a short time.

  The magneto-optical spectrum measurement method according to claim 5 is the magneto-optical spectrum measurement method according to claim 4, wherein the magnetic field is applied in a direction perpendicular to the surface of the sample in the correlation determination step. When it is determined that there is a correlation between the absolute value of the Kerr rotation angle and the angle of the incident light polarization plane, a third measurement step, a fourth calculation step, a second correlation determination step, and an origin determination step are performed. It is preferable to include and execute. Here, when it is determined that there is a correlation in the correlation determination step, the second measurement control step based on the polarization modulation method is not performed. In such a case, it is necessary to calculate the spectrum of the magneto-optical characteristic. As a predetermined operation mode in the magneto-optical spectrum spectrometer, the spectrum of the magneto-optical characteristic can be obtained by an operation mode in which the first measurement control step by the rotating polarizer method is repeatedly performed. The third measurement step, the fourth calculation step, the second correlation determination step, and the origin determination step performed when it is determined that there is a correlation in the correlation determination step is one of such operation modes, It is set as a mode for searching for the origin of the magneto-optical effect.

  According to such a procedure, in the magneto-optical spectrum measurement method, in the third measurement step, the direction of the magnetic field applied to the sample is measured in the plane of the sample in the measurement using the rotating polarizer method by the control means. Then, the voltage value is measured by the voltmeter set in a direction parallel to the light incident surface. Then, in the fourth calculation step, the calculation means calculates the absolute value of the Kerr rotation angle from the measurement value measured in the third measurement step. Then, in the second correlation determination step, the absolute value of the Kerr rotation angle calculated by the calculation means using the measurement value measured in the third measurement step and the angle of the incident light polarization plane Determine the presence or absence of correlation. When it is determined that there is a correlation in the second correlation determination step, the origin determination step includes a vertical Kerr effect or linear dichroism contribution in the magneto-optical effect of the sample by the calculation means. It is determined that As a result, according to the magneto-optical spectrum measurement method, it is determined that there is a correlation between the absolute value of the Kerr rotation angle and the angle of the incident light polarization plane in the correlation determination step, and in principle it does not result from the polar Kerr effect. In the new third measurement step, measurement is performed while controlling the magnetization direction of the sample in an arrangement in which the longitudinal Kerr effect appears in principle, and the presence or absence of correlation is again determined based on this measurement value. As a result of the examination, if there is a correlation, it can be determined that the Kerr rotation angle is caused by the vertical Kerr effect or linear dichroism.

  Further, the magneto-optical spectrum measurement method according to claim 6 is the magneto-optical spectrum measurement method according to claim 5, further comprising a fourth measurement step, a fifth calculation step, following the origin determination step, It is preferable to execute including a third correlation determination step and a second origin determination step.

  According to such a procedure, in the magneto-optical spectrum measurement method, in the fourth measurement step, in the measurement using the rotating polarizer method, the direction of the magnetic field applied to the sample is set within the plane of the sample. The voltage is set by the voltmeter with the normal direction of the light incident surface. Then, in the fifth calculation step, the calculation means calculates the absolute value of the Kerr rotation angle from the measurement value measured in the fourth measurement step. Then, in the third correlation determination step, the calculation means calculates the absolute value of the Kerr rotation angle calculated using the measurement value measured in the fourth measurement step and the angle of the incident light polarization plane. Determine the presence or absence of correlation. If it is determined that there is a correlation in the third correlation determination step, it is determined in the second origin determination step that a linear dichroism contribution is included in the magneto-optical effect of the sample by the calculation means. judge. Thereby, according to the magneto-optical spectrum measurement method, the Kerr rotation angle calculated from the measurement value measured in the third measurement step in the origin determination step may be caused by the vertical Kerr effect or linear dichroism. If it is determined, in a new fourth measurement step, measurement is performed while controlling the magnetization direction of the sample in an arrangement in which the longitudinal Kerr effect does not appear in principle, and the presence or absence of correlation is again determined based on this measurement value. As a result of the examination, if there is a correlation, it can be determined that the Kerr rotation angle is caused by linear dichroism.

  The program according to claim 7 is a program for causing a computer to execute the magneto-optical spectrum measurement method according to any one of claims 4 to 6. By being configured in this way, a computer in which this program is installed can realize each function based on this program.

  According to the invention of claim 1, claim 4 or claim 7, the magneto-optical spectrum spectrometer is an absolute value of the Kerr rotation angle which is a signal observed as a magneto-optical effect due to the polar Kerr effect of the sample. Can be measured. In addition, the magneto-optical spectrum spectrometer uses a conversion value using the absolute value of the Kerr rotation angle accurately measured by the rotating polarizer method for the Kerr rotation angle spectrum measured in a relatively short time by the polarization modulation method. Since the multiplication is performed uniformly, the signal observed as the magneto-optical effect can be measured efficiently. Therefore, the origin of the MO signal can be determined, and the measurement of the MO spectrum and the calibration of the MO signal can be easily realized.

  According to the invention described in claim 2 or claim 5, in the magneto-optical spectrum spectrometer, as the origin of the MO signal, the Kerr rotation angle is caused by the polar Kerr effect, or other than the polar Kerr effect, that is, the longitudinal Kerr effect. Alternatively, it can be distinguished whether it is caused by linear dichroism. Therefore, when the magneto-optical signal of the sample is caused by the longitudinal Kerr effect or linear dichroism, the magneto-optical spectrum of the sample can be obtained by a suitable measurement method other than the polarization modulation method.

  According to the invention described in claim 3 or claim 6, in the magneto-optical spectrum spectrometer, whether the Kerr rotation angle is caused by the polar Kerr effect, the vertical Kerr effect, or the linear dichroism as the origin of the MO signal. Can be distinguished. Therefore, when the magneto-optical signal of the sample is caused by linear dichroism, the magneto-optical spectrum of the sample can be obtained by a suitable measurement method other than the polarization modulation method.

It is a figure which shows typically the structure which was set as the surface direct magnetic field application arrangement | positioning in the magneto-optical spectrum spectrometer which concerns on embodiment of this invention. It is a figure which shows typically the structure made into the in-plane magnetic field application arrangement | positioning in the magneto-optical spectrum spectrometer which concerns on embodiment of this invention. It is a block diagram which shows the structural example of the information processing apparatus shown in FIG. It is a flowchart which shows the flow of operation | movement of the magneto-optical spectrum spectrometer which concerns on embodiment of this invention. It is a flowchart which shows an example of the operation mode of the magneto-optical spectrum spectrometer which concerns on embodiment of this invention. It is a figure which shows typically the positional relationship of the direction of the magnetic field applied to a sample, and the advancing direction of the polarized light which injects into a sample, (a) is the arrangement | positioning which applies a magnetic field to the surface direction of a sample, (b) is An arrangement in which a magnetic field is applied in the in-plane A direction (parallel to the incident plane of polarized light) of the sample, and (c) is an arrangement in which a magnetic field is applied in the in-plane B direction (normal direction of the incident plane of polarized light) of the sample. Show. It is a measurement example which concerns on this invention, Comprising: It is a graph which shows the relationship between the rotation angle of the 2nd linear polarizing plate with a rotation mechanism at the time of using a rotating polarizer method, and the voltage signal observed with the digital voltmeter. It is a measurement example which concerns on this invention, Comprising: It is a graph which shows the relationship between the magnetic field applied to the sample at the time of using a rotating polarizer method, and the rotation angle of the polarization plane obtained from the observed MO signal. It is a measurement example which concerns on this invention, Comprising: It is a graph which shows the relationship between the wavelength of the polarized light irradiated to the sample at the time of using a rotating polarizer method, and the rotation angle of the polarization plane obtained from the observed MO signal. FIG. 4 is a measurement example according to the present invention, and is a graph showing the relationship between the wavelength of polarized light applied to a sample when the rotating polarizer method is used and the rotation angle of the polarization plane based on the magnetic characteristics calculated from the MO signal It is. It is a measurement example which concerns on this invention, Comprising: The rotation angle of the 1st linearly polarizing plate with a rotation mechanism at the time of using a rotation polarizer method, and the rotation angle of the polarization plane by the magnetic characteristic calculated | required by calculation from MO signal It is a graph which shows a relationship. It is a measurement example which concerns on this invention, Comprising: It is a graph which shows the spectrum of the rotation angle of the polarization plane by the magnetic characteristic calculated | required by calculation from the MO signal observed when the polarization modulation method was used. It is a measurement example which concerns on this invention, Comprising: It is a graph which shows the magneto-optical spectrum which calibrated the spectrum of the rotation angle shown in FIG.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.
[1. Outline of configuration of magneto-optical spectrum spectrometer]
A magneto-optical spectrum spectrometer 1 measures a spectrum of magneto-optical characteristics of a sample. As shown in FIG. 1, a light source 2, a spectrometer 3, a first linearly polarizing plate 4, and a photoelastic modulation. A device 5, a magnetic field applying means 6, a second linearly polarizing plate 7, a light detecting means 8, a digital voltmeter 9, a lock-in amplifier 10, and an information processing device 20.

  The information processing apparatus 20 includes, for example, a general personal computer including an arithmetic device such as a CPU (Central Processing Unit), a storage device such as a memory or a hard disk, and an interface device that transmits and receives various types of information to and from the outside. The computer includes a control unit 30, a storage unit 40, and a calculation unit 50.

The control means 30 is composed of a CPU and a memory, and controls an operation including switching of the wavelength of light of a predetermined wavelength that is split by the spectroscope 3 at a preset timing.
The storage means 40 is composed of a storage device such as a RAM (Random Access Memory) or ROM (Read Only Memory) or a hard disk, and voltage values (rotation polarization) respectively measured by the digital voltmeter 9 and the lock-in amplifier 10. The child method measurement value 41 and the polarization modulation method measurement value 42) are stored.
The calculation means 50 is composed of a CPU and a memory, and calculates the Kerr rotation angle as the magneto-optical characteristic of the sample based on the voltage value stored in the storage means 40.

  Here, the light source 2, the spectroscope 3, the first linearly polarizing plate 4, the photoelastic modulator 5, the magnetic field applying unit 6, the second linearly polarizing plate 7, the light detecting unit 8, the digital voltmeter 9, and the lock-in amplifier 10. Are arranged so as to be the arrangement of the measurement system when a conventionally known polarization modulation method is used. That is, with this arrangement, light having a predetermined wavelength emitted from the light source 2 and dispersed by the spectroscope 3 is incident on the first linear polarizing plate 4, and the polarized light that has passed through the first linear polarizing plate 4 is photoelastic. The light enters the modulator 5. The circularly polarized light modulated by the photoelastic modulator 5 is applied to the sample F to which a magnetic field is applied by the magnetic field applying means 6. The reflected light reflected by the sample F enters the second linearly polarizing plate 7, and the reflected light of the sample that has passed through the second linearly polarizing plate 7 is detected as an electrical signal by the light detection means 8. The electric signal detected by the light detection means 8 is input to the digital voltmeter 9 and the lock-in amplifier 10 and measured as a voltage value. The transmitted light that has passed through the sample F may be incident on another linearly polarizing plate, and the transmitted light of the sample that has passed through the linearly polarizing plate may be detected as an electrical signal by the light detection means.

  In the magneto-optical spectrum spectrometer 1 according to the present embodiment, the control unit 30 switches between a conventionally known polarization modulation method measurement system and a conventionally known rotational polarizer method measurement system, and the calculation unit 50 is described later. Thus, in addition to the calculation function of both measurement methods, it is different from the conventional measurement apparatus in that it has a function of determining the origin of the magneto-optical effect. Further, in order to switch between the measurement system of the polarization modulation method and the measurement system of the rotating polarizer method, each linearly polarizing plate 4, 7 can be adjusted so that the angle of the polarization plane becomes a predetermined value by rotation. It is different from the conventional measurement system in that it is a linearly polarizing plate.

[2. Details of each part of the measurement system of the magneto-optical spectrum spectrometer]
The light source 2 is not particularly limited as long as it emits light having a wavelength within a range that can be used for each of the linearly polarizing plates 4 and 7. For example, a halogen lamp such as a xenon lamp can be used.
The spectroscope 3 splits light from the light source 2 and is not particularly limited. For example, a diffraction grating type spectroscope can be used. The spectroscope 3 is configured to be able to switch the wavelength value of the light to be split based on a control signal from the control means 30. A higher-order light blocking filter or the like may be used.

The first linear polarizing plate 4 converts the light separated by the spectroscope 3 into linearly polarized light, and is disposed on the incident light side of the sample F. The second linear polarizing plate 7 converts the light reflected by the sample F into linearly polarized light. Each of the linear polarizing plates 4 and 7 is formed, for example, by mounting a general linear polarizing plate on a polarizer holder with an automatic angle adjustment function.
Although not shown, the polarizer holder with an automatic angle adjustment function includes, for example, a frame-like substrate that holds the outer periphery of the linearly polarizing plate, a rotation shaft that includes a pinion gear that rotates the substrate, and the control means 30. Rotation drive means for driving the rotation shaft based on the control signal, and a rotary encoder for detecting the rotation angle of the substrate. The linear polarizing plates 4 and 7 may be the same.

Hereinafter, the angle of the incident light polarization plane, which is the polarization plane in the first linear polarizing plate 4, is denoted as φ _1, and the angle of the polarization plane in the second linear polarizing plate 7 is denoted as φ ₂ . The angles φ ₁ and φ ₂ indicate angles around an axis with the traveling direction of light as an axis.
In the measurement using the rotating polarizer method, the angles φ ₁ and φ ₂ indicate values that are changed in the range of 0 to 180 °, for example.
In the measurement using the polarization modulation method, the angle φ ₁ is fixed at 45 ° and the angle φ ₂ is fixed at 0 °. For example, when the angle φ ₁ on the polarization plane of the first linearly polarizing plate 4 is fixed at 45 °, the light passing through the first linearly polarizing plate 4 becomes linearly polarized light inclined by 45 ° with respect to the subsequent photoelastic modulator 5. Become. If the angle φ ₂ is fixed at 0 °, the light that has passed through the second linearly polarizing plate 7 becomes linearly polarized light that is not inclined with respect to the subsequent light detection means 8.
In the present embodiment, as shown in FIG. 1, the light that has passed through the first linearly polarizing plate 4 is condensed by the condenser lens 11 and can be irradiated to the photoelastic modulator 5.

  The photoelastic modulator 5 is arranged in the middle of the path of the light irradiated to the sample F, and outputs the incident light by alternately switching between the left-handed circularly polarized light and the right-handed circularly polarized light at a predetermined modulation frequency. is there. The photoelastic modulator 5 includes an isotropic transparent optical material and a piezoelectric element, and is configured so that the polarization modulation function can be switched between an on state and an off state based on a control signal from the control unit 30. ing. A signal having a value twice the modulation frequency of the photoelastic modulator 5 is input to the lock-in amplifier 10 as a reference signal. The modulation frequency of the photoelastic modulator 5 can be set to 50 kHz, for example.

  The magnetic field applying unit 6 applies a predetermined magnetic field to the sample F, and includes, for example, an electromagnet. Based on a control signal from the control unit 30, the applied magnetic field is turned on / off and the magnitude of the applied magnetic field. It can be switched. By applying a magnetic field from the magnetic field applying means 6 to the sample F, the direction of magnetization in the sample F can be changed. In the example shown in FIG. 1, the magnetic field applying unit 6 </ b> A is disposed so that a perpendicular magnetic field can be applied to the sample F. In the example shown in FIG. 2, the magnetic field applying means 6 </ b> B is arranged so that an in-plane magnetic field can be applied to the sample F. In the present embodiment, the magnetic field applying unit 6 includes a driving unit (not shown) for switching the arrangement of the electromagnets, and the magnetic field applying unit 6A and the magnetic field applying unit according to the operation mode indicated by the control signal from the control unit 30. 6B is described as being configured to be switchable.

  The light detection means 8 detects light reflected by the sample F and passed through the second linearly polarizing plate 7, for example, from a semiconductor photo detector such as a photomultiplier tube or a general photodiode. Composed. The reflected light (electric signal) detected by the light detection means 8 is input to the digital voltmeter 9 and the lock-in amplifier 10.

  The digital voltmeter (voltmeter) 9 has an input (IN) connected to the light detection means 8 and an output (OUT) connected to the input (IN) of the information processing apparatus 20. The digital voltmeter 9 is a general voltmeter capable of digital processing. Hereinafter, the voltage value detected by the digital voltmeter 9 is expressed as V. This voltage value V indicates a measurement value for each angle of the polarization plane in each of the linearly polarizing plates 4 and 7 in the measurement system using the rotating polarizer method.

  The lock-in amplifier 10 has an input (IN) connected to the light detection means 8, a reference (REF) connected to the photoelastic modulator 5, and an output (OUT) connected to the input (IN 2) of the information processing device 20. Has been. The lock-in amplifier 10 detects a voltage value of a frequency component equal to a reference signal (a signal twice the modulation frequency) input from the photoelastic modulator 5 from the electric signal output from the light detection means 8. Hereinafter, the voltage value detected by the lock-in amplifier 10 is expressed as ΔV. In the measurement system using the polarization modulation method, each calculation result of ΔV / V indicates a measurement value using the polarization modulation method.

[3. Details of each part of information processing apparatus of magneto-optical spectrum spectrometer]
FIG. 3 is a block diagram illustrating a configuration example of the information processing apparatus illustrated in FIG.
The control means 30 includes a first measurement control means 31 and a second measurement control in order to realize fully automatic MO signal observation at a predetermined wavelength using the rotating polarizer method and MO spectrum measurement by the polarization modulation method. Means 32.
The first measurement control means 31 uses a rotating polarizer method in which the polarization modulation function of the photoelastic modulator 5 is turned off and the angles φ ₁ and φ ₂ of the polarization planes are respectively changed in the linearly polarizing plates 4 and 7. Then, control for measuring the voltage value detected by the voltmeter 9 is performed, and each measured value for each angle of the polarization plane is recorded in the storage means 40.

  In the measurement system using the rotating polarizer method, since the polarization modulation function of the photoelastic modulator 5 is in an off state, the reference signal is not output to the lock-in amplifier 10, and the lock-in amplifier 10 does not substantially function. Only the voltage value V measured by the digital voltmeter 9 is used by the information processing apparatus 20. Further, the photoelastic modulator 5 irradiates the sample F by allowing incident light to pass through without being modulated, although the polarization modulation function is off. Each measured value for each angle of the polarization plane in each of the linear polarizers 4 and 7 using this rotating polarizer method is stored as a rotating polarizer method measured value 41 in the storage means 40.

Although the detailed procedure of the measuring method of the rotating polarizer method will be described later, the angles φ ₁ and φ ₂ of the polarization plane in each of the linearly polarizing plates 4 and 7 are uniformly changed at a predetermined pitch (Δφ). Note that the pitch Δφ and the number of measurements thereof may be appropriately set in consideration of desired measurement accuracy and measurement time. For example, the pitch Δφ may be set to 1, 2 ° for fine measurement, and the pitch Δφ may be set to 15, 30 ° for coarse measurement.

In the measurement using the rotating polarizer method, one predetermined wavelength may be used as the wavelength of light, but it is preferable to use a plurality of types of wavelengths by changing the wavelength. As the wavelength value, for example, when selecting from the range of visible light, if it is one, for example, 500 nm or 700 nm, and if it is two, both may be selected. Since the measurement time becomes longer as the types of wavelengths are increased, the number of wavelengths to be used is appropriately set in advance.
Although depending on the measurement point of the angle of the polarization plane in each of the linear polarizing plates 4 and 7, when one type of wavelength is used in the rotating polarizer method, a measurement time of about 15 to 20 minutes is required as an example. On the other hand, in the polarization modulation method, since the linear polarizing plates 4 and 7 are fixed, the spectrum of the magneto-optical signal can be measured in about 30 minutes as an example. Therefore, in order to shorten the measurement time, the type of wavelength used for measurement is preferably 5 or less.

  The second measurement control means 32 changes the wavelength of light split by the spectroscope 3 by fixing the polarization modulation function of the photoelastic modulator 5 and fixing the linearly polarizing plates 4 and 7 at a predetermined angle. Control for measuring voltage values respectively detected by the voltmeter 9 and the lock-in amplifier 10 is performed using the polarization modulation method, and the measured values are recorded in the storage means 40. In the measurement system using the polarization modulation method, since the polarization modulation function of the photoelastic modulator 5 is on, the reference signal is output to the lock-in amplifier 10 and the voltage value ΔV measured by the lock-in amplifier 10 and the digital volt. The information processing apparatus 20 uses the voltage value V measured by the meter 9. Further, since the polarization modulation function is on, the photoelastic modulator 5 modulates the incident light and irradiates the sample F. The measurement values measured for each wavelength using this polarization modulation method are stored as polarization modulation method measurement values 42 in the storage means 40.

Here, as an angle in the polarization plane of the linearly polarizing plate 4 and 7, fixed angle phi ₁ to 45 °, to fix the angle phi ₂ to 0 °. In the measurement using the polarization modulation method, for example, when the wavelength of light is selected from the range of visible light, it is uniformly changed at a predetermined pitch in the range of blue (about 450 nm) to red (about 750 nm). The pitch may be appropriately set in consideration of desired measurement accuracy and measurement time. The pitch may be 1 nm, for example.

The computing unit 50 includes a first calculating unit 51, a correlation determining unit 52, a second calculating unit 53, and a third calculating unit 54.
The first calculation means 51 calculates the absolute value of the Kerr rotation angle at a predetermined wavelength based on the rotational polarizer method measurement value 41 stored as the measurement value for each angle of the polarization plane in the storage means 40. Calculate according to. Although details of the calculation method will be described later, this calculated value is stored in the storage means 40 as the Kerr rotation angle absolute value 43.

The correlation discriminating means 52 is based on the Kerr rotation angle absolute value 43 stored in the storage means 40 and the rotational polarizer method measurement value 41 stored in the storage means 40, and the Kerr rotation angle absolute value 43 and the incident light. to determine the presence or absence of a correlation between the angle phi ₁ of the polarization plane. When the correlation determination unit 52 determines that there is no correlation, the correlation determination unit 52 notifies the second calculation unit 53 to that effect. On the other hand, when it is determined that there is a correlation, the information processing apparatus 20 executes processing according to a preset operation mode described later.

Here, that there is a correlation between the Kerr rotation angle absolute value 43 and the angle phi ₁ of the incident light polarization plane refers to the case where also increased Kerr rotation angle, for example, in accordance with the angle phi ₁ of the incident light polarization plane is increased. From another point of view, when the measured values are visualized so that the horizontal axis indicates the angle φ ₁ of the incident light polarization plane and the vertical axis indicates the Kerr rotation angle, if there is a correlation, a graph that rises to the right is obtained. When there is no correlation, a graph substantially parallel to the horizontal axis is obtained.

When the correlation determining means 52 determines that there is no correlation between the Kerr rotation angle absolute value 43 and the angle φ ₁ of the incident light polarization plane, the second calculating means 53 measures each wavelength stored in the storage means 40. The spectrum of the Kerr rotation angle of the sample is calculated based on the measured polarization modulation method value 42. Although details of the calculation method will be described later, this calculated value is stored in the storage means 40 as the Kerr rotation angle spectrum 44.

  The third calculation means 54 obtains a conversion value for adapting the Kerr rotation angle value in the Kerr rotation angle spectrum 44 stored in the storage means 40 to the Kerr rotation angle absolute value 43 stored in the storage means 40, and determines the Kerr rotation. By multiplying the Kerr rotation angle value in the angular spectrum 44 by the converted value, the corrected Kerr rotation angle spectrum is calculated as the magneto-optical characteristic spectrum of the sample. Although details of the calculation method will be described later, this calculated value is stored as an MO spectrum 45 in the storage means 40 and displayed on an output device such as a liquid crystal display (not shown).

[4. Flow of operation of magneto-optical spectrum spectrometer]
Next, the flow of operations of the magneto-optical spectrum spectrometer 1 will be described with reference to FIG. 4 (see FIGS. 1 and 3 as appropriate). As an example, a sample of a plane perpendicular magnetization film is assumed.
<Step S1>
In step S1, a magnetic field having a predetermined magnitude is applied in the direction perpendicular to the surface of the sample F by the magnetic field applying means 6A. This step S1 is only formally separated from step S2 for the description of the preset operation mode to be described later, and is actually included in step S2. In addition, in the preset operation mode to be described later, a description will be given as a mode in which the direction of the magnetic field applied to the sample is changed.

<Step S2>
In step S <b> 2, the magneto-optical spectrum spectrometer 1 uses the first measurement control unit 31 to measure the voltage value V detected from the reflected light of the sample in the measurement system using the rotating polarizer method. That is, when the sample F is irradiated with light of a predetermined wavelength, the voltage value V measured by the digital voltmeter 9 is recorded for each polarization plane angle in each of the linearly polarizing plates 4 and 7.

  More specifically, in step S2, the following operation is performed. That is, in step S2, the first measurement control means 31 first turns off the polarization modulation function of the photoelastic modulator 5. Further, the position of the linearly polarizing plates 4 and 7 is adjusted by rotating the linearly polarizing plates 4 and 7. Then, by passing the light obtained from the light source 2 through the spectroscope 3, monochromatic light having a narrow spectral width is extracted. Then, the light split by the spectroscope 3 is passed through the first linear polarizing plate 4 to be linearly polarized light. Then, the light transmitted through the first linearly polarizing plate 4 is irradiated onto the sample F, and the reflected light is passed through the second linearly polarizing plate 7 and observed by the light detecting means 8. Then, the voltage signal obtained from the light detection means 8 is observed with the digital voltmeter 9, and the obtained voltage value is recorded with the information processing device 20.

≪Measurement method of rotating polarizer method≫
In order to determine the MO signal by the processing described later, this rotational polarizer method measurement method can be realized by the following procedures (B1) to (B7).
(B1) is set to default values phi ₁ ⁰ the angle phi ₁ of the polarization plane of the first linear polarization plate 4.
Moreover, setting the angle phi ₂ to the initial set value phi ₂ ⁰ of the polarization plane of the second linear polarization plate 7.
(B2) In this state, the initial value V ₀ of the voltage value V _n observed by the digital voltmeter 9 is recorded, counting as the 0th time when only the second linearly polarizing plate 7 is rotated.
(B3) While maintaining the angle φ ₁ in the first linearly polarizing plate 4 at the current value, the angle φ ₂ of the polarization plane in the second linearly polarizing plate 7 is increased from the current value by a predetermined pitch Δφ ₂ to obtain the angle (φ ₂ ⁰ + Δφ ₂ ).
(B4) 1 time count when the state of the angle phi ₁ ⁰ and the angle (φ ₂ ⁰ + Δφ ₂₎ to the set respectively B3 in each linear polarization plate 4 and 7, to rotate only the second linear polarization plate 7 Then, the voltage value V ₁ observed by the digital voltmeter 9 is recorded.
(B5) Similarly, when counting only the second time when only the second linear polarizing plate 7 is rotated (n is a natural number), the angle φ ₁ in the first linear polarizing plate 4 is maintained at the current value, The voltage value V _n (φ ₁ , φ ₂ ) observed by the digital voltmeter 9 is recorded after setting the angle φ ₂ of the polarization plane of the second linearly polarizing plate 7 to φ ₂ ⁰ + nΔφ. The number of measurements and Δφ are determined in consideration of the required measurement accuracy and measurement time.
(B6) Through the measurement, the relationship between the voltage value V _n (φ ₁ , φ ₂ ) and the polarization plane angle φ ₂ of the second linearly polarizing plate 7 is obtained (n = 1, 2,...).
(B7) The angle φ ₁ of the polarization plane in the first linearly polarizing plate 4 is replaced with φ ₁ + nΔφ ₁ (n is a natural number), and (B1) to (B6) are repeated.
Thus, the voltage value V _n (φ ₁ , φ ₂ ) is recorded for each angle φ ₁ of the polarization plane in the first linearly polarizing plate 4. These recorded many voltage values are simply expressed as V (φ ₁ , φ ₂ ) below.

<Step S3>
Next, in step S3, the magneto-optical spectrum spectrometer 1 calculates the absolute value of the Kerr rotation angle as the MO signal based on the voltage value obtained for each rotation angle by the first calculation unit 51 of the calculation unit 50, respectively. It is calculated corresponding to the voltage value of.
The first calculation means 51 analyzes the voltage value V (φ ₁ , φ ₂ ) measured as an electric signal in step S2 to obtain the Kerr rotation angle.
As an example, when it is assumed that the sample F exhibits the Kerr effect at the angle φ _K , the detection voltage value is theoretically V ₀ cos ² (φ ₁ −φ ₂ + φ _K ) based on the principle of the rotating polarizer method. Since the measured value should be equal to this theoretical value, the following equation holds:
V (φ ₁ , φ ₂ ) = V ₀ cos ² (φ ₁ −φ ₂ + φ _K ) (1)
Therefore, the first calculation means 51 numerically analyzes the observed voltage value V (φ, φ ₂ ) using the formula (1). From the phase information of the voltage value V obtained from the analysis and the values of the angles φ ₁ and φ ₂ used for the measurement, the value of the angle φ _K that is assumed to exhibit the Kerr effect can be directly determined. Specific examples will be described later.

<Step S4>
Next, in step S <b> 4, the magneto-optical spectrum spectrometer 1 determines whether or not there is a correlation between the obtained Kerr rotation angle and the angle of the incident light polarization plane by the correlation determination unit 52 of the calculation unit 50. Here, the angle of the polarization plane of the incident light is the angle φ ₁ in the first linearly polarizing plate 4 used for the measurement, and the correlation determining unit 52 measures the angle φ _K assumed to indicate the calculated Kerr effect. It depends on the angle phi ₁ determines whether or not the used for.

<Step S5>
In step S4, if the Kerr rotation angle is determined to not be dependent on the angle phi ₁ of the incident light polarization plane (step S4: No), since the magneto-optical effect is due to the polar Kerr effect, magneto-optical spectroscopy device 1 Then, the voltage values V and ΔV detected from the reflected light of the sample are measured by the second measurement control means 32 in the measurement system using the polarization modulation method (step S5). That is, when the position of each linearly polarizing plate 4, 7 is fixed and the sample F is irradiated with polarized light, the voltage value V measured by the digital voltmeter 9 and the voltage value ΔV measured by the lock-in amplifier 10. Are recorded for each wavelength of light. When the Kerr rotation angle does not depend on the angle φ ₁ of the incident light polarization plane, the reason why the magneto-optic effect is caused by the polar Kerr effect will be described later.

More specifically, in step S5, the operation is as follows. That is, in step S5, the second measuring control means 32 first, 45 ° angle phi ₁ of the polarization plane of the first linear polarizing plate 4, the angle phi ₂ of the polarization plane of the second linear polarization plate 7 is 0 ° The polarization modulation function of the photoelastic modulator 5 is turned on. Then, by passing the light obtained from the light source 2 through the spectroscope 3, monochromatic light having a narrow spectral width is extracted. Then, the light split by the spectroscope 3 is passed through the first linear polarizing plate 4 to obtain linearly polarized light inclined by 45 ° with respect to the photoelastic modulator 5. Then, the light transmitted through the first linearly polarizing plate 4 is passed through the photoelastic modulator 5 so as to perform high-speed modulation with clockwise polarized light and counterclockwise polarized light. The modulation frequency at this time is f _1. Order to synchronize the modulation period and a lock-in amplifier 10 of a photoelastic modulator 5, as a reference signal of the lock-in amplifier 10 inputs a signal of twice the frequency of the modulation frequency f _1. Here, in order to obtain the Kerr effect, the reference signal is a signal having a frequency twice the modulation frequency f _1. However, when obtaining circular dichroism, the reference signal has the same frequency as the modulation frequency f ₁ . It may be a signal. Then, the sample F is irradiated with the polarized light that has passed through the photoelastic modulator 5, and the reflected light passes through the second linear polarizing plate 7 and is observed by the light detection means 8. Then, the voltage signal obtained from the light detection means 8 is observed by the digital voltmeter 9 and the lock-in amplifier, respectively, and the obtained voltage values (V, ΔV) are recorded by the information processing device 20.

≪Measurement method of polarization modulation method≫
In order to measure the MO spectrum, the measurement method of the polarization modulation method can be realized by, for example, the following procedures (C1) to (C7). This polarization modulation method is described in detail in Non-Patent Document 1.
(C1) and the set wavelength of the spectroscope 3, and setting the wavelength of the photoelastic modulator 5 is set to the initial wavelength lambda _0.
(C2) In the photoelastic modulator 5, the set wavelength is set to the set wavelength (initial wavelength λ ₀ ), the modulation mode is set to ¼ wavelength, the modulation frequency is set to f _1, and the lock-in amplifier 10 sets the reference frequency to Let 2f be ₁ . In the following, although the set wavelength is sequentially switched to the set wavelength in the photoelastic modulator 5, the modulation mode and the modulation frequency are fixed, and the reference frequency of the lock-in amplifier 10 is also fixed.
(C3) In the state of C2, the voltage value ΔV ₀ is calculated using the lock-in amplifier 10 when the sample F is irradiated with the light of the initial wavelength λ ₀ by counting the 0th time when the set wavelength is changed. At the same time, the voltage value V ₀ is measured using the digital voltmeter 9.
(C4) The set wavelengths of the spectroscope 3 and the photoelastic modulator 5 are set to λ ₁ = (λ ₀ + Δλ).
(C5) In the state of C4, the voltage value ΔV ₁ , V ₁ is measured using the lock-in amplifier 10 and the digital voltmeter 9 counting as the first time when the set wavelength is changed.
(C6) Similarly, when the set wavelength is counted as the nth time (n is a natural number), the set wavelengths of the spectroscope 3 and the photoelastic modulator 5 are set to λ _n = (λ ₀ + nΔλ). Thereafter, the voltage values ΔV _n and V _n are measured using the lock-in amplifier 10 and the digital voltmeter 9.
(C7) Through the measurement, the relationship between the voltage value (ΔV _n , V _n ) and the wavelength is obtained.

<Step S6>
Next, in step S <b> 6, the magneto-optical spectrum spectrometer 1 calculates the spectrum of the Kerr rotation angle from the voltage value obtained for each wavelength by the second calculator 53 of the calculator 50. The second calculation means 53 analyzes the data (ΔV _n , V _n ) obtained as electrical signals in step S5 to obtain the Kerr rotation angle spectrum 44. Here, the Kerr rotation angle is proportional to ΔV / V. The proportionality constant is not yet determined, and the absolute value of the rotation angle is not determined here.

<Step S7>
Therefore, in step S7, the third calculation unit 54 of the calculation unit 50 uses the second calculation unit 53 to calculate the Kerr rotation angle absolute value 43 calculated by the first calculation unit 51 in order to determine the absolute value of the rotation angle. A conversion value adapted to the calculated Kerr rotation angle spectrum 44 is obtained. The third calculation means 54 obtains a conversion value by normalizing the Kerr rotation angle absolute value 43 obtained for at least one wavelength with the rotation angle of the same wavelength in the Kerr rotation angle spectrum 44. When a plurality of conversion values are obtained using a plurality of wavelengths in the Kerr rotation angle absolute value 43, for example, the average is set as the final conversion value. Then, the third calculation means 54 multiplies the calculated spectrum (Kerr rotation angle spectrum 44) by the converted value to calculate the calibrated MO spectrum (step S7).

<Step S8>
In step S4, when the magneto-optical spectrum spectrometer 1 determines that the Kerr rotation angle depends on the angle of the incident light polarization plane by the correlation determination unit 52 of the calculation unit 50 (step S4: Yes), a predetermined operation is performed. Processing according to the mode is performed (step S8).

Here, the predetermined operation mode is a mode in which, for example, the MO spectrum is calculated by repeatedly performing the measurement of the rotating polarizer method by the first measurement control unit 31 and the first calculation unit 51 of the information processing apparatus 20. A rotational polarizer method measurement mode can be mentioned.
Further, since the magneto-optical effect is a linear sum of the polar Kerr effect, the vertical Kerr effect, and the linear dichroism, for example, the observed magneto-optical effect is caused by other than the polar Kerr effect (vertical Kerr effect or linear dichroism). There may be provided a mode for determining whether or not, a mode for determining whether or not the origin of the magneto-optical effect is caused by linear dichroism, and the like.
In this embodiment, as an example of the operation mode, an origin search mode for identifying a magneto-optical effect other than the polar Kerr effect (an origin search mode for the magneto-optical effect) is determined in advance. This origin search mode can be performed by, for example, the first measurement control unit 31, the first calculation unit 51, and the correlation determination unit 52 of the information processing apparatus 20.

[5. Origin search mode]
<Decision principle of origin search mode>
Here, an example of the origin search mode is shown in the flowchart of FIG. Before explaining each process of this flowchart, the principle of determination will be described with reference to FIG.
FIG. 6A is a diagram schematically showing the positional relationship between the direction of the magnetic field applied to the sample and the traveling direction of the polarized light incident on the sample, and FIG. 6A applies the magnetic field in the direction perpendicular to the surface of the sample. The arrangement to be shown is shown. If it arrange | positions like Fig.6 (a), it is possible to detect that the polar Kerr effect appears. In FIG. 6A, the sample F is in the form of a film and is placed on the XY plane, and the case where the polarized light L incident obliquely is reflected at a point O on the surface of the sample F is illustrated. At this time, the magnetic field applying means 6 causes the magnetization vector M of the sample F (hereinafter simply referred to as magnetization M) to have the magnetization M oriented in the normal direction (Z-axis direction) of the XY plane as shown in the figure. Measurement is performed in a controlled state. That is, the magnetic field applying means 6A shown in FIG.

Moreover, the broken-line surface shown in FIG. 6A represents the polarization plane in the first linearly polarizing plate 4. In this example, the polarization plane of the first linearly polarizing plate 4 intersects the X axis. If the angle of the polarization plane in the first linear polarizing plate 4 is changed by 90 °, for example, from the state indicated by the broken line, the polarization plane in the first linear polarizing plate 4 intersects the Y axis. Thus, changing the angle of the polarization plane in the first linear polarizing plate 4 is to rotate the polarization plane in the first linear polarizing plate 4 about the direction of the magnetization M of the sample F as an axis. Any angle does not affect the orientation of the magnetization M. That is, if the angle φ _K assumed to exhibit the Kerr effect does not depend on the angle φ ₁ of the polarization plane in the first linearly polarizing plate 4 used for the measurement, the magneto-optical effect at this time is the polar Kerr effect. It is thought to be caused.

  FIG. 6B and FIG. 6B respectively show arrangements in which a magnetic field is applied in the in-plane direction of the sample. In the arrangement shown in FIGS. 6B and 6C, the magnetic field applying unit 6B shown in FIG. Further, when arranged as shown in FIG. 6B, it is possible to detect the appearance of the vertical Kerr effect or linear dichroism. On the other hand, if it arrange | positions like FIG.6 (c), it cannot detect that the vertical Kerr effect appears.

  The difference between FIG. 6B and FIG. 6A is controlled by the magnetic field applying means 6B so that the direction of the magnetization M of the sample F is in the in-plane direction of the XY plane and in the X-axis direction. This is a point where the measurement is performed in the state. Here, the in-plane direction of the XY plane and the X-axis direction indicate an in-plane direction of the XY plane and a direction parallel to the light incident surface. Hereinafter, this direction is referred to as an in-plane A direction.

  Further, the difference between FIG. 6C and FIG. 6A is that the orientation of the magnetization M of the sample F is in the in-plane direction of the XY plane and in the Y-axis direction (hereinafter referred to as in-plane B) by the magnetic field applying means 6B. The measurement is performed in a state controlled so as to be called a direction. Here, the in-plane direction of the XY plane and the Y-axis direction are in-plane directions of the XY plane and indicate the normal direction of the light incident surface. Hereinafter, a direction orthogonal to the in-plane A direction is referred to as an in-plane B direction.

In FIG. 6B, the polarization plane indicated by the broken line intersects with the X axis and is aligned with the direction of the magnetization M of the sample F, so that the signal observed at this time is a vertical Kerr effect or linear dichroism. It is due. When the polarization plane indicated by the broken line is rotated, the observed signal changes according to the rotation angle. That is, since the angle φ _K assumed to exhibit the Kerr effect depends on the angle φ ₁ of the polarization plane in the first linearly polarizing plate 4, the magneto-optical effect at this time is caused by the vertical Kerr effect or linear dichroism. It is thought to be.

Incidentally, when the angle of the polarization plane of the first linearly polarizing plate 4 is changed by 90 ° from the state shown in FIG. 6B, the state is substantially equivalent to the state shown in FIG. Therefore, the signal observed when the angle of the polarization plane is changed by 90 ° from the state shown in FIG. 6B is not due to the vertical Kerr effect. That is, when the angle φ _K assumed to exhibit the Kerr effect in the observation signal depends on the angle φ ₁ of the polarization plane of the first linearly polarizing plate 4, the measurement is further performed in the state shown in FIG. In the case where the angle φ _K still depends on the angle φ ₁ of the polarization plane, the magneto-optical effect at this time is considered to be due to linear dichroism.

<Flow of operation in origin search mode>
The flowchart of FIG. 5 is constructed according to the above-described determination principle. The flow of operation in the origin search mode of the magneto-optical effect will be described with reference to FIG. 5 (see FIGS. 1, 3, 4 and 6 as appropriate). In this origin search mode, first, in step S <b> 11, the magneto-optical spectrum spectrometer 1 sets the application direction of the magnetic field to the in-plane A direction by the first measurement control unit 31.

  In step S 12, the magneto-optical spectrum spectrometer 1 measures the voltage value V with the digital voltmeter 9 by the first measurement control unit 31 and calculates the Kerr rotation angle by the first calculation unit 51. Here, the 1st measurement control means 31 performs a measurement, changing the magnitude | size of a magnetic field within the range of the magnitude | size of the predetermined magnetic field. The range of the magnitude of the magnetic field is determined as the magnitude that the vertical Kerr effect appears.

  In step S13, similarly to step S4, the magneto-optical spectrum spectrometer 1 has a correlation between the Kerr rotation angle obtained by the correlation determination unit 52 of the calculation unit 50 and the angle of the incident light polarization plane. It is determined whether or not. When there is a correlation (step S13: Yes), the correlation determination unit 52 determines that the magneto-optical effect is caused by the vertical Kerr effect or linear dichroism, and ends the simple search process (step S14). At this time, the correlation determination unit 52 outputs a message indicating that the magneto-optical effect is caused by the vertical Kerr effect or linear dichroism to an output unit (not shown). On the other hand, when there is no correlation in step S13 (step S13: No), the correlation determination means 52 performs an error process (step S19). At this time, the correlation determination unit 52 may output a message indicating that the origin of the magneto-optical effect is unknown to an output unit (not shown).

  Then, as an option following step S14 of the simple search process, when it is desired to search in more detail the origin of the magneto-optical effect, in step S15, the magneto-optical spectrum spectrometer 1 uses the first measurement control unit 31 to The application direction of the magnetic field is set to the in-plane B direction. In step S <b> 16, the magneto-optical spectrum spectrometer 1 measures the voltage value V with the digital voltmeter 9 by the first measurement control unit 31, and calculates the Kerr rotation angle by the first calculation unit 51.

  In step S17, similarly to step S13, the magneto-optical spectrum spectrometer 1 has a correlation between the Kerr rotation angle obtained by the correlation determination unit 52 of the calculation unit 50 and the angle of the incident light polarization plane. It is determined whether or not. When there is a correlation (step S17: Yes), the correlation determination unit 52 determines that the magneto-optical effect is caused by linear dichroism (step S18). At this time, the correlation determination unit 52 may output a message indicating that the magneto-optical effect is due to linear dichroism to an output unit (not shown).

  On the other hand, when there is no correlation in step S17 (step S17: No), the correlation determination means 52 performs an error process (step S19). At this time, the correlation determination unit 52 may output a message indicating that the origin of the magneto-optical effect is unknown to an output unit (not shown). In the detailed search, in the case of No in step S17, the possibility that the cause of the magneto-optical effect may not be the sole cause of the polar Kerr effect, the vertical Kerr effect, and the linear dichroism is denied. It is not possible. Further, in the case of No in step S17, the correlation determination unit 52 may output the determination result in step S14 again to an output unit (not shown) without performing error processing. This is because in a simple search, in the case of No in step S17, there is no conflict with the determination result in step S14 that is caused by the vertical Kerr effect or linear dichroism. Note that whether to end with a simple search or to perform a detailed search can be changed as appropriate according to the required measurement time and measurement accuracy.

[6. MO signal observation example]
A result of observing an MO signal using a GdFe thin film as a sample will be described using the magneto-optical spectrum spectrometer 1 shown in FIG. The sample GdFe thin film is a plane perpendicular magnetization film, and magnetization is reversed when an external magnetic field _Hext is applied in the direction perpendicular to the plane. An MO signal observed using the magneto-optical spectrum measurement method of the present embodiment is denoted as θ _K. Here, K is a suffix indicating the Kerr rotation angle. This θ _K represents the rotation angle due to the magneto-optical effect, and theoretically corresponds to the angle φ _K assumed to exhibit the Kerr effect in the above-described equation (1).

<Measurement principle of MO signal>
The MO signal θ _K is a superposition of a signal component (this is expressed as Δθ _K (M)) caused by the magnetic characteristics of the sample and a non-magnetic signal component (this is expressed as Δθ _NM ) of the sample. It is a combination. Here, M represents a magnetic characteristic of the sample, and NM represents a non-magnetic characteristic. That is, when considering the magnetic characteristics of the sample, for example, when the direction of the external magnetic field applied when the magnetization is reversed is M, the MO signal θ _K (M) can be expressed by Expression (2). .

θ _K (M) = Δθ _K (M) + Δθ _NM (2)

The information desired to be measured is the signal component Δθ _K (M) resulting from the magnetic characteristics of the sample, and can be determined using the following relationship or the like. Here, if the direction of the external magnetic field applied before the magnetization of the sample is reversed is expressed as −M, the magnetization is reversed in the direction before the magnetization of the sample is reversed in the state before the magnetization of the sample is reversed. Since it rotates, the first term Δθ _K (M) on the right side of Equation (2) has the relationship of Equation (3).

Δθ _K (M) = − Δθ _K (−M) (3)

When the direction of the external magnetic field applied to the sample is the state before magnetization reversal (-M), the relationship of equation (4) is obtained in the same manner as equation (2). Moreover, when the relationship of Formula (3) is used, Formula (4) can be rewritten into Formula (5). Further, by subtracting the sides of equation (5) from equation (2), equation (6) is obtained. To summarize this, the signal component Δθ _K (M) resulting from the magnetic characteristics in the MO signal θ _K , which is information desired to be obtained by measurement, is expressed by Expression (7a).

θ _K (−M) = Δθ _K (−M) + Δθ _NM (4)
θ _K (−M) = − Δθ _K (M) + Δθ _NM (5)
θ _K (M) −θ _K (−M) = 2Δθ _K (M) (6)
Δθ _K (M) = (θ _K (M) −θ _K (−M)) / 2 Formula (7a)

Therefore, when the direction of the external magnetic field applied when the magnetization of the sample is reversed is M, the left side θ _K (M) of Equation (3) is observed as an MO signal, and is applied before the magnetization of the sample is reversed. The right side θ _K (−M) of the equation (3) was observed as an MO signal when the direction of the external magnetic field was −M. In the following, the MO signal, which is an observation signal, is omitted by omitting K and simply expressed as θ (M) or θ (−M), and the information to be obtained is omitted and is simply expressed as Δθ _K. That is, Equation (7a) is rewritten as Equation (7b).

Δθ _K = (θ (M) −θ (−M)) / 2 Formula (7b)

<Observation of MO signal using the rotating polarizer method>
≪φ ₂ dependence of voltage signal≫
FIG. 7 shows an example of observation of an MO signal using a rotating polarizer method with a GdFe thin film as a sample. In the graph of FIG. 7, the horizontal axis indicates the angle φ ₂ of the polarization plane of the second linearly polarizing plate 7, and the vertical axis indicates the voltage signal (voltage value V) observed by the digital voltmeter 9 in arbitrary units (arbitrary units: a .U.).

Innumerable circles in this graph are experimental results of voltage values V (φ ₁ , φ ₂ ), and indicate MO signals θ (M) or θ (−M) for each angle φ ₂ . The solid line in the form of a cosine function is an analysis result, and is a result obtained by fitting the experimental result by the first calculation means 51 based on the equation (1). As shown in FIG. 7, the observed V (φ ₁ , φ ₂ ) is reproduced very well using the above equation (1), and the value of the angle φ _K that is assumed to exhibit the Kerr effect can be directly determined. It was. Here, referred to as the rotation angle theta _K that the angle phi _K in accordance with the measurement principles of the formula (2) or later MO signal. Here, the notation of M is omitted. The rotation angle θ _K corresponds to the calculated absolute value of the Kerr rotation angle.

≪Dependence of θ _K on external magnetic field≫
FIG. 8 shows an example of the rotation angle calculated from the MO signal using the rotating polarizer method using a GdFe thin film as a sample. In the graph of FIG. 8, the horizontal axis indicates the external magnetic field applied to the sample by the magnetic field applying means 6A. In addition, about the unit of a magnetic field, it can convert in 1 [Oe] = 799.577 [A / m]. In addition, the vertical axis of the graph of FIG. 8 indicates the rotation angle θ _K calculated by the first calculation means 51 in ° (degree: deg.). Note that the rotation angle shown on the vertical axis is a correctly calibrated value.

In this experiment, the rotational polarizer method was applied by changing the wavelength of the light separated by the spectroscope 3 at a pitch of 50 nm in the range of 500 to 700 nm. In the graph of FIG. 8, the magnetic field dependence of the rotation angle θ _K observed when the light wavelength is 500 nm is indicated by a circle, and the magnetic field dependence of the rotation angle θ _K observed when the light wavelength is 700 nm. Indicated by square marks. Further, the magnetic field applying means 6A applied the sample while increasing the negative magnetic field from the negative magnetic field. As shown in the graph of FIG. 8, a remarkable change in the rotation angle θ _K was observed with the magnetization reversal from 0 kOe to 0.5 kOe.

Therefore, next, the notation of M, which was intentionally omitted at the rotation angle θ _K in accordance with the expression of the equation (7b), is added, and in the graph of FIG. 8, the sample corresponds to the state before the magnetization reversal. A signal from −2.0 kOe to 0.0 kOe is expressed as θ _K (−M), and a signal from 0.5 kOe to 2.0 kOe corresponding to the state after the sample is reversed in magnetization is expressed as θ _K. It was designated as (M).

≪Wavelength dependence of θ _K (M) and θ _K (−M) ≫
Then, in the graph of FIG. 8, the wavelength of light is set to 500 nm and 700 nm, and the magnetic field dependence of the observed rotation angle θ _K is fitted with a linear function, and then the intercepts are θ _K (−M) and θ _K ( The results of M) are shown in FIG. In the graph of FIG. 9, the horizontal axis indicates the wavelength of light dispersed by the spectroscope 3, and the vertical axis indicates the same rotation angles θ _K (−M) and θ _K (M) as in the graph of FIG. In the graph of FIG. 9, the rotation angle θ _K (−M) is indicated by a square mark, and the rotation angle θ _K (M) is indicated by a circle. These results correspond to the MO signals θ (−M) and θ (M) shown on the right side of the equation (7b). Moreover, these results are the results obtained by appropriately changing the angles of the linearly polarizing plates 4 and 7. FIG. 10 shows Δθ _K , which is a result determined by substituting the experimental results shown in the graph of FIG. 9 into the equation (7b).

≪Δθ _K wavelength dependence≫
In the graph of FIG. 10, the horizontal axis indicates the wavelength of light as in FIG. 9, and the vertical axis indicates information to be obtained and indicates the rotation angle Δθ _K caused by the magnetic characteristics of the sample in the MO signal. In the graph of FIG. 10, the rotation angle Δθ _K is indicated by dots, and the lines above and below the dots indicate the range of standard deviations of errors. Thus, the wavelength dependence of Δθ _K was determined by using the rotating polarizer method. Although measurement by the rotating polarizer method takes time, there is an advantage that the absolute value of the MO signal, that is, the absolute value of Δθ _K can be accurately determined. The value of the rotation angle Δθ _K represented by the wavelength-specific dots in the graph corresponds to the Kerr rotation angle absolute value 43 that is the calculation result of the first calculation means 51.

Φ ₁ dependence of «Δθ _K »
In the graph of FIG. 10, the relationship between the measurement result of the rotation angle Δθ _K observed at a wavelength of 500 nm and the polarization plane angle φ ₁ of the first linearly polarizing plate 4 at that time is shown in FIG. In FIG. 11, the horizontal axis indicates the angle φ ₁ of the polarization plane in the first linearly polarizing plate 4, and the vertical axis indicates the rotation angle Δθ _K. In the graph of FIG. 11, the rotation angle Δθ _K is indicated by dots, and the lines above and below the dots indicate the range of standard deviations of errors. As seen in FIG. 11, the rotation angle Δθ _K does not depend on the angle φ ₁ of the polarization plane of the first linearly polarizing plate 4. This suggests that the MO signal observed in this sample is dominated by the polar Kerr effect, and is consistent with the fact that the sample is a perpendicular magnetic film. Therefore, in the measurement method of this embodiment, the correlation determination unit 52 of the calculation unit 50 determines that the observed MO signal is due to the polar Kerr effect, and then performs measurement using the polarization modulation method. .

When the MO signal is dominated by the polar Kerr effect as shown in the graph of FIG. 11, a straight line substantially parallel to the horizontal axis is obtained by connecting the rotation angles Δθ _K for each angle φ ₁ . On the other hand, when the MO signal is governed by the vertical Kerr effect or linear dichroism, if a similar graph is created, the rotation angle depends on φ ₁ . Therefore, whether or not the MO signal is dominated by the polar Kerr effect becomes obvious when the relationship between the observed Kerr rotation angle and the angle φ ₁ of the polarization plane of the first linearly polarizing plate 4 is graphed.

<Observation of MO spectrum using polarization modulation method>
≪Δθ _K wavelength dependence≫
Next, the MO spectrum was observed by using the polarization modulation method under the same conditions using the GdFe thin film observed by the rotating polarizer method. Here, in order to align the magnetization direction of the sample, measurement was performed by applying an external magnetic field of 1 kOe to the sample by the magnetic field applying means 6A. The measurement results are shown in FIG. The graph of FIG. 12 is a graph similar to the graph of FIG. 10, the horizontal axis indicates the wavelength of light, and the vertical axis indicates the rotation angle Δθ _K. However, in the graph of FIG. 12, since the value of the rotation angle Δθ _K is not calibrated, it is shown in arbitrary units (au). In the polarization modulation method, since the MO spectrum can be measured efficiently, signals at many wavelengths can be acquired, but it is difficult to determine the absolute value of the MO signal.

  In the measurement method of the present embodiment, in order to normalize the absolute value of the MO signal, the third calculation means 54 of the calculation means 50 uses the Kerr rotation angle absolute value stored in the storage means 40 corresponding to the graph of FIG. A conversion value that matches the value 43 with the Kerr rotation angle spectrum 44 stored in the storage means 40 corresponding to the graph of FIG. The result of calibrating the Kerr rotation angle spectrum 44 is shown in FIG. 13 as the MO spectrum.

In the graph of FIG. 13, a solid line indicates the wavelength dependence of [Delta] [theta] _K was observed by the polarization modulation method, square marks showing the wavelength dependence of [Delta] [theta] _K observed by rotating polarizer method. According to the measurement method of this embodiment, the MO signal determined by the rotating polarizer method is used to normalize the absolute value of the MO signal, and an MO spectrum in which the absolute value is calibrated can be obtained. It was also possible to directly determine that the MO signal is dominated by the polar Kerr effect.

  According to the magneto-optical spectrum spectrometer 1 of the present embodiment, the measurement system using the rotational polarizer method and the measurement system using the polarization modulation method are configured to be switchable, and at least one predetermined using the rotational polarizer method. Since the MO signal observation at the wavelength and the MO spectrum measurement by the polarization modulation method can be realized automatically, the measurement time of the signal observed as the magneto-optical effect can be reduced.

  Further, according to the magneto-optical spectrum spectrometer 1 and the measurement method of the present embodiment, the MO spectrum is calibrated with the MO signal determined by the rotating polarizer method by calibrating the MO spectrum obtained by the polarization modulation method. Can be obtained.

  Further, according to the magneto-optical spectrum spectrometer 1 and the measurement method of the present embodiment, after confirming that the MO signal determined by the rotating polarizer method is caused by the polar Kerr effect, the MO spectrum obtained by the polarization modulation method is obtained. As a result of analysis, unlike the conventional case, it can be confirmed that the MO spectrum calibrated using the two measurement methods represents the Kerr rotation angle due to the polar Kerr effect rather than the vertical Kerr effect and linear dichroism. Even if the MO signal determined by the rotating polarizer method cannot be confirmed to be due to the polar Kerr effect, the origin can be searched for due to the vertical Kerr effect or linear dichroism.

  Further, according to the magneto-optical spectrum spectrometer 1 and the measurement method of the present embodiment, information storage such as an MO disk, a Faraday element indispensable for stable optical communication, a three-dimensional display using a hologram, and the like By examining the MO effect of magnetic materials correctly and efficiently in various applied technologies in which the magneto-optical effect is used, it is expected to promote their research and development.

  As mentioned above, although this invention was demonstrated based on embodiment, this invention is not limited to this. For example, in this embodiment, the reflected light reflected by the sample F is passed through the second linearly polarizing plate 7 and observed by the light detection means 8. However, the transmitted light that has passed through the sample F is observed by the second linearly polarizing plate 7. The same effect can be obtained even if the light detection means 8 is used for the observation.

  Further, in the present embodiment, a sample of a surface perpendicularly magnetized film is assumed, and in step S1, a magnetic field having a predetermined magnitude is applied in the direction perpendicular to the surface of the sample F by the magnetic field applying unit 6A. A sample of the inner magnetized film may be used, and the direction of the magnetic field applied in step S1 can be similarly measured with an in-plane magnetic field.

  In the measurement method of the present embodiment, measurement using the polarization modulator method is performed after the measurement by the rotating polarizer method, the calculation of the Kerr rotation angle, and the determination of the correlation between the Kerr rotation angle and the angle of the incident light polarization plane are finished. However, the calculation process and the determination process may be performed after the measurement by the rotating polarizer method and the measurement using the polarization modulation method are finished.

  For example, the control device of the magneto-optical spectrum spectrometer can be realized by operating a general computer by a program that functions as the control unit 30 and the calculation unit 50 described above. This program can be distributed via a communication line, or can be written on a recording medium such as a DVD or a CD-ROM for distribution.

  The present invention is applied to various application technologies in which the magneto-optical effect is used, such as information storage such as MO disk, Faraday element indispensable for stable optical communication, and three-dimensional display using hologram. it can.

DESCRIPTION OF SYMBOLS 1 Magneto-optical spectrum spectrometer 2 Light source 3 Spectrometer 4 1st linear polarizing plate 5 Photoelastic modulator 6 Magnetic field application means 7 2nd linear polarizing plate 8 Photodetection means 9 Digital voltmeter 10 Lock-in amplifier 20 Information processing apparatus 30 Control Means 31 First measurement control means 32 Second measurement control means 40 Storage means 41 Rotating polarizer method measured value (measured value using rotating polarizer method)
42 Measurement value of polarization modulation method (measurement value using polarization modulation method)
43 Absolute value of car rotation angle (absolute value of car rotation angle)
44 Kerr rotation angle spectrum (Kerr rotation angle spectrum)
45 MO spectrum (absolute value of spectrum)
50 Calculation means 51 First calculation means 52 Correlation determination means 53 Second calculation means 54 Third calculation means F Sample

Claims (7)

A light source arranged as a measurement system using a polarization modulation method for measuring a spectrum of a magneto-optical characteristic of a sample, a spectroscope, a first linearly polarizing plate, a photoelastic modulator, a magnetic field applying unit, and a second linearly polarized light A plate, a light detection means, a voltmeter, a lock-in amplifier, a control means for controlling an operation including switching of wavelengths of light of a predetermined wavelength that is split by the spectroscope at a preset timing, and the bolt Magneto-optics comprising storage means for storing voltage values respectively measured by a meter and the lock-in amplifier, and arithmetic means for calculating a Kerr rotation angle as a magneto-optical characteristic of the sample based on the stored voltage values In a spectral spectrometer,
Each of the linear polarizing plates is a linear polarizing plate with a rotation mechanism that can be adjusted so that the angle of the polarization plane becomes a predetermined value by rotation,
The control means includes
For measuring the voltage value detected by the voltmeter using a rotating polarizer method in which the polarization modulation function of the photoelastic modulator is turned off and the angle of the polarization plane is changed in each linearly polarizing plate. First measurement control means for performing control and recording each measurement value for each angle of the polarization plane in the storage means;
The voltmeter using a polarization modulation method in which the polarization modulation function of the photoelastic modulator is on, each linearly polarizing plate is fixed at a predetermined angle, and the wavelength of light dispersed by the spectrometer is changed. And second measurement control means for performing control for measuring voltage values respectively detected by the lock-in amplifier and recording each measurement value in the storage means,
The computing means is
The absolute value of the Kerr rotation angle at the predetermined wavelength is calculated on the basis of the measured values for each angle of the polarization plane in each linearly polarizing plate using the rotating polarizer method stored in the storage means. A calculation means;
Correlation determining means for determining whether or not there is a correlation between the absolute value of the Kerr rotation angle at the predetermined wavelength and the angle of the incident light polarization plane that is the polarization plane of the first linearly polarizing plate;
When it is determined that there is no correlation between the absolute value of the Kerr rotation angle and the angle of the polarization plane of the incident light, the Kerr rotation of the sample is performed based on the measured value using the polarization modulation method stored in the storage means. A second calculating means for calculating a spectrum of the corners;
A conversion value that matches the value of the Kerr rotation angle in the spectrum calculated by the second calculation unit with the absolute value of the Kerr rotation angle calculated by the first calculation unit is obtained, and the value of the Kerr rotation angle in the spectrum is obtained. A third calculating means for calculating the spectrum of the calibrated Kerr rotation angle as the spectrum of the magneto-optical characteristic of the sample by multiplying the converted values respectively;
A magneto-optical spectrum spectrometer characterized by comprising: The magnetic field applying means includes
A surface perpendicular magnetic field applying means for applying a magnetic field in a direction perpendicular to the surface of the sample;
An in-plane magnetic field applying means for applying a magnetic field in the in-plane direction of the sample,
The correlation determining means of the calculating means is
If there is a correlation between the absolute value of the Kerr rotation angle when the magnetic field is applied in the direction perpendicular to the sample and the angle of the incident light polarization plane, the light is incident in the in-plane direction of the sample. Further, it is determined whether or not there is a correlation between the absolute value of the Kerr rotation angle calculated using a measured value when a magnetic field is applied parallel to the surface and the angle of the incident light polarization plane. 2. The magneto-optical spectrum spectrometer according to claim 1, wherein in some cases, it is determined that the magneto-optical effect of the sample includes a vertical Kerr effect or a contribution of linear dichroism. The correlation determining means of the calculating means is
The correlation between the absolute value of the Kerr rotation angle calculated using the measured value when the magnetic field is applied in parallel to the incident surface of light in the in-plane direction of the sample and the angle of the incident light polarization plane is In some cases, the absolute value of the Kerr rotation angle calculated using a measured value when a magnetic field is applied in the in-plane direction of the sample and in the normal direction of the light incident surface, and the incident light polarization The presence or absence of correlation with the angle of the surface is further determined, and if there is a correlation between them, the determination that the contribution of the vertical Kerr effect is included is reversed, and the magneto-optical effect of the sample is linear dichroism The magneto-optical spectrum spectrometer according to claim 2, wherein it is determined that the contribution is included. A light source arranged as a measurement system using a polarization modulation method for measuring a spectrum of a magneto-optical characteristic of a sample, a spectroscope, a first linearly polarizing plate, a photoelastic modulator, a magnetic field applying unit, and a second linearly polarized light A magneto-optical spectrum measurement method in a magneto-optical spectrum spectrometer comprising a plate, a light detection means, a voltmeter, a lock-in amplifier, a control means, a storage means, and a calculation means,
Each of the linear polarizing plates is a linear polarizing plate with a rotation mechanism that can be adjusted so that the angle of the polarization plane becomes a predetermined value by rotation,
By the control means,
In order to measure the voltage value detected by the voltmeter by using the rotating polarizer method in which the polarization modulation function of the photoelastic modulator is turned off and the angle of the polarization plane is changed in each linearly polarizing plate. And a first measurement control step for recording each measurement value for each angle of the polarization plane in the storage means,
By the computing means,
The absolute value of the Kerr rotation angle at the predetermined wavelength is calculated on the basis of the measured values for each angle of the polarization plane in each linearly polarizing plate using the rotating polarizer method stored in the storage means. A calculation step;
A correlation determination step of determining whether or not there is a correlation between an absolute value of a Kerr rotation angle at the predetermined wavelength and an angle of an incident light polarization plane that is a polarization plane in the first linear polarizing plate;
By the control means,
When it is determined that there is no correlation between the absolute value of the Kerr rotation angle and the angle of the incident light polarization plane, the polarization modulation function of the photoelastic modulator is turned on, and each linearly polarizing plate is turned to a predetermined angle. The measurement value is controlled by measuring the voltage value detected by the voltmeter and the lock-in amplifier using a polarization modulation method that changes the wavelength of light split by the spectroscope. A second measurement control step for recording the data in the storage means;
By the computing means,
A second calculation step of calculating a spectrum of the Kerr rotation angle of the sample based on a measurement value using the polarization modulation method stored in the storage unit;
A conversion value that matches the value of the Kerr rotation angle in the spectrum calculated in the second calculation step with the absolute value of the Kerr rotation angle calculated in the first calculation step is obtained, and the value of the Kerr rotation angle in the spectrum is obtained. A third calculation step for calculating the spectrum of the calibrated Kerr rotation angle as the spectrum of the magneto-optical characteristic of the sample by multiplying each of the conversion values by:
A magneto-optical spectrum measurement method comprising: When it is determined in the correlation determination step that there is a correlation between the absolute value of the Kerr rotation angle when a magnetic field is applied in a direction perpendicular to the surface of the sample and the angle of the incident light polarization plane, the control means By
In the measurement using the rotating polarizer method, a voltage value is measured by the voltmeter by setting the direction of the magnetic field applied to the sample to be in the plane of the sample and parallel to the light incident surface. While performing the measurement step,
By the computing means,
A fourth calculation step of calculating an absolute value of the Kerr rotation angle from the measurement value measured in the third measurement step;
A second correlation determination step for determining whether or not there is a correlation between the absolute value of the Kerr rotation angle calculated using the measurement value measured in the third measurement step and the angle of the incident light polarization plane;
An origin determination step for determining that the magneto-optical effect of the sample includes a vertical Kerr effect or a contribution of linear dichroism when it is determined that there is a correlation in the second correlation determination step;
The magneto-optical spectrum measurement method according to claim 4, wherein the magneto-optical spectrum measurement method is performed. Following the origin determination step, the control means further
In the measurement using the rotating polarizer method, the direction of the magnetic field applied to the sample is set in the normal direction of the light incident surface within the surface of the sample, and the voltage value is measured by the voltmeter. While performing 4 measurement steps,
By the computing means,
A fifth calculation step of calculating an absolute value of the Kerr rotation angle from the measurement value measured in the fourth measurement step;
A third correlation determination step for determining whether or not there is a correlation between the absolute value of the Kerr rotation angle calculated using the measurement value measured in the fourth measurement step and the angle of the incident light polarization plane;
If it is determined in the third correlation determination step that there is a correlation, the determination that the vertical Kerr effect contribution is included is reversed, and the magneto-optical effect of the sample includes a contribution of linear dichroism. A second origin determination step for determining that the
The magneto-optical spectrum measurement method according to claim 5, wherein the magneto-optical spectrum measurement method is performed.   The program for making a computer perform the magneto-optical spectrum measuring method as described in any one of Claims 4 thru | or 6.

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