JPH08184559A - Method and apparatus for evaluating orientation of magnetic recording medium - Google Patents

Abstract

PURPOSE: To evaluate the orientation of the surface part of a magnetic recording medium. CONSTITUTION: Light Ri emitted from a semiconductor laser 13 is passed through a polarizing plate 14 to be a p-polarized light. A magnetic recording medium 10 is set on a stage 15 so that the longitudinal direction of the medium 10 and the direction of p-polarized light Ri are included in one plane. Irradiation of the medium 10 with the p-polarized light Ri and reception of a reflected light Rr by a photodiode 22 are repeated while varying the incident angle β. A first complex permittivity ε0 is determined from the relationship of the intensity of reflected light and the incident angle β. The stage 15 is then turned by 90 deg. so that the longitudinal and vertical directions of the medium 10 and the direction of the p-polarized light Ri are included in one plane and a second complex permittivity εs is determined similarly. Such an evaluation is made that the larger the difference between the complex part εj0 of the first complex permittivity ε0 and the complex part εjs of the second complex permittivity εs , the higher the orientation.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an apparatus and method for evaluating the degree of orientation of a magnetic material used in a magnetic recording medium such as a magnetic tape or a floppy disk.

[0002]

BACKGROUND OF THE INVENTION As shown in FIG. 8 (A), an atom in a normal state has a nucleus 71 at its center, and an electron 72 around the nucleus 71.
There is. A model of electrons 72 in the dielectric is shown in FIG. As shown in FIG. 9, electrons 72 are bound in the dielectric.

When an electric field E is applied to the electrons 72, FIG.
As shown in, the electrons 72 move in the direction opposite to the direction of the electric field E.
This makes an apparent dipole (polarization) as shown in Fig. 8 (C). The above is the outline of the phenomenon called atomic polarization. In the crystal as well, polarization is similarly generated when the charge distribution is displaced by the external electric field.

In general, a magnetic material is a fine particle aggregate or a polycrystalline body having an anisotropic crystal structure in order to improve magnetic characteristics (microscopically, due to electron spin in the crystal). The structure of each anisotropic crystal has a polarization characteristic that depends on the crystal axis. As a conclusion, the polarization characteristics of the magnetic material as an aggregate reflect the distribution of individual anisotropic crystal axes and the magnetic anisotropy characteristics. The property can be derived.

It is said that the more the crystal axes are aligned in one direction, the higher the orientation degree is (see FIG. 11), and the more the orientation is, the lower the orientation degree is.

Among magnetic recording media, a magnetic tape, for example, records information while traveling in one direction, so that the degree of orientation of the magnetic material is preferably high. On the other hand, among magnetic recording media, for example, a floppy disk records information while rotating, so that it is preferable that the degree of orientation of the magnetic material is low. The degree of orientation of magnetic recording media must be changed according to the type, and it is important to evaluate the degree of orientation.

As a method of evaluating the orientation degree, for example, VS
The M. (Vibrating Sample Magnetmeter) method is known. The VSM method is a method for evaluating the orientation degree by moving the magnetic recording medium for evaluating the orientation degree in the vicinity of the coil and detecting the change in the number of magnetic flux lines passing through the coil.

However, in the evaluation of the degree of orientation by the VSM method, not only the surface of the magnetic material coated on the magnetic recording medium but also the degree of orientation of the inner magnetic material is evaluated.

On the other hand, since the surface portion of the magnetic recording medium is close to the magnetic head, its magnetic characteristics have a great influence on the reproduced signal. In addition, a recording magnetic loop is formed on the surface of a magnetic recording medium for high density and high frequency recording.
As can be seen from these facts, what is important in the orientation degree of the magnetic material in the magnetic recording medium is the orientation degree of the surface of the magnetic material in the magnetic recording medium.

[0010]

DISCLOSURE OF THE INVENTION An object of the present invention is to make it possible to evaluate the degree of orientation of the surface of a magnetic material of a magnetic recording medium relatively easily.

The method of evaluating the degree of orientation of a magnetic recording medium according to the present invention is orthogonal to the surface of the magnetic recording medium which is the object to be inspected,
In addition, two planes orthogonal to each other are set, the light beam is irradiated to the magnetic recording medium in one plane, the reflected light from the magnetic recording medium is received, and the incident angle between the light beam irradiation and the light reception is set. The first complex permittivity of the magnetic recording medium in the direction parallel to the above-mentioned one plane is calculated based on the reflected light intensity of the received reflected light and the incident angle when the reflected light intensity is obtained by repeatedly changing it. And irradiating the magnetic recording medium with a light beam in the other of the planes,
Based on the reflected light intensity of the received reflected light and the incident angle when the reflected light intensity is obtained, the reflected light from the magnetic recording medium is received, and the light beam irradiation and the light reception are repeated by changing the incident angle. Then, the second complex dielectric constant of the magnetic recording medium in the direction parallel to the other plane is calculated.

The magnetic recording medium orientation evaluation apparatus according to the present invention is orthogonal to the surface of the magnetic recording medium to be inspected,
And a first light source that sets two planes orthogonal to each other and irradiates a light beam into the magnetic recording in one of the planes, and a light beam to the magnetic recording medium in the other plane of the set plane. A second light source for irradiating the magnetic recording medium, a light receiving element for receiving reflected light from the magnetic recording medium, an incident angle of the light beam emitted from the first light source and the second light source to the magnetic recording medium, Incident angle changing means, irradiation of the light beam from the first light source to the magnetic recording medium, and reception of reflected light by the light receiving element are obtained by changing the incident angle using the incident angle changing means. First calculating means for calculating the first complex dielectric constant of the magnetic recording medium in the direction parallel to the one plane based on the respective reflected light intensities and the incident angles at which the reflected light intensities are obtained. Also, the respective reflections obtained by irradiating the magnetic recording medium with the light beam from the second light source and receiving the reflected light by the light receiving element by changing the incident angle using the incident angle changing means. Second calculation means for calculating the second complex dielectric constant of the magnetic recording medium in the direction parallel to the other plane based on the incident angle when the light intensity and the reflected light intensity are obtained. Is characterized by.

It is generally known that the degree of orientation appears as a change in complex permittivity ε. Therefore, the degree of orientation of the magnetic recording medium can be evaluated using the complex dielectric constant ε as an index.

The complex permittivity can be detected if the complex refractive index is known when the light beam is applied to the magnetic recording medium for examining the degree of orientation. The complex refractive index is obtained by irradiating the magnetic recording medium with a light beam and receiving the reflected light by the light receiving element by changing the incident angle. It can be calculated based on the incident angle. Therefore, the complex permittivity can be calculated based on the reflected light intensity and the incident angle when the reflected light intensity is obtained.

As shown in FIG. 11, when the orientation of the magnetic recording medium is high, the directionality of the magnetic needle MN changes vertically between the longitudinal direction of the magnetic recording medium 10 and the vertical direction. Therefore, there is a large difference between the magnitude of the complex permittivity obtained by irradiating the magnetic recording medium with the light beam in the longitudinal direction and the complex permittivity obtained by irradiating the magnetic beam with the light beam in the direction perpendicular to the longitudinal direction.
On the other hand, when the degree of orientation of the magnetic recording medium is low as shown in FIG. 10, the directionality of the magnetic needle MN does not change much between the longitudinal direction and the vertical direction of the magnetic recording medium 10. Therefore, the difference between the magnitude of the complex permittivity obtained by irradiating the magnetic recording medium with the light beam in the longitudinal direction and the magnitude of the complex permittivity obtained by irradiating the magnetic beam with the light beam in the longitudinal direction is small. .

From the above, the degree of orientation of the magnetic recording medium is determined by irradiating a light beam from one plane direction when two planes which are orthogonal to the surface of the magnetic recording medium and orthogonal to each other are set. This can be understood from the difference between the magnitude of the obtained complex permittivity and the magnitude of the complex permittivity obtained by irradiating the light beam from the other plane direction.

The present invention utilizes the relationship between the degree of orientation of such a magnetic recording medium and the complex dielectric constant.

According to the present invention, the magnetic recording medium is irradiated with the light beam in the one plane, the first complex permittivity is calculated based on the reflected light intensity and the incident angle, and the other plane is calculated. The magnetic recording medium is irradiated with a light beam in the inside, and the second complex permittivity is calculated based on the reflected light intensity and the incident angle. The degree of orientation of the magnetic recording medium is evaluated from the calculated first complex permittivity and second calculated permittivity. For example, it is evaluated that the larger the difference between the first complex permittivity and the second complex permittivity, the higher the degree of orientation of the magnetic recording medium.

According to the present invention, since the complex permittivity of the surface of the magnetic recording medium is calculated based on the reflection intensity of the light beam and the incident angle, it is possible to evaluate the degree of orientation on the surface portion of the magnetic recording medium. it can. In this way, it is possible to evaluate the degree of orientation of the surface portion of the magnetic recording medium, which has a great influence on the reproduction signal.

The one plane is, for example, parallel to the longitudinal direction of the magnetic recording medium.

Since the light beam is used, the degree of orientation can be evaluated without destroying the magnetic recording medium. Furthermore, the degree of orientation can be evaluated even during the production process of the magnetic recording medium.

The first complex permittivity and the second complex permittivity can be obtained by using the least square method.

The coefficient of the imaginary part of the first complex permittivity,
It is preferable to evaluate that the larger the difference from the coefficient of the imaginary part of the second complex dielectric constant, the higher the degree of orientation of the magnetic recording medium. This is because the coefficient of the real part of the complex permittivity depends on the incident angle of linearly polarized light, and the coefficient changes according to the change of the incident angle.

In order to evaluate the degree of orientation using the coefficient of the real part of the complex permittivity, it will be necessary to standardize.

The light beam with which the magnetic recording medium is irradiated is preferably linearly polarized light. This is because the difference between the first complex permittivity and the second complex permittivity clearly appears when the degree of orientation is high by using linearly polarized light. Further, the use of linearly polarized light makes it relatively easy to calculate the first complex permittivity and the second complex permittivity.

When the magnetic recording medium is irradiated with linearly polarized light, it is preferably p-polarized light. Since an inflection point occurs in reflected light intensity when p-polarized light is used, errors can be reduced even if the first complex permittivity and the second complex permittivity are calculated using the least square method. That's why.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the configuration of a magnetic recording medium orientation degree evaluation device according to the present invention.

The orientation degree evaluation apparatus shown in FIG. 1 utilizes the fact that the complex refractive index differs depending on the orientation degree of the magnetic recording medium. Here, the complex refractive index ε is expressed by Equation 1.

[0029]

## EQU1 ## ε = ε ₀ n ² _j2 Equation 1

Here, ε ₀ is the dielectric constant of vacuum, and n _j2 is the complex refractive index of the medium in which light is refracted.

[0031] Figure 7, the refractive index n of a medium 1 of refractive index n ₁
When light enters the _second medium 2, reflecting, state of refraction is shown.

Considering the refractive index vector (refractive index in which the directionality of the light ray in the medium is related) in FIG. 7, the vector component of the refractive index vector n _V1 in the medium 1 is n _V1.
= Represented by _{(n 1 sinβ 1, 0,} n 1 cosβ 1).

On the other hand, the x component of the vector component of the refractive index vector n _V2 of the light refracted in the medium 2 is the x component (n ₁ si) of the refractive index vector n _V1 of the incident light in the medium 1.
It is known to be equal to nβ ₁ ). Also, considering that the z component (component in the depth direction) of the refractive index vector n _V2 is due to the fact that the absorption of light depends only on the distance z along the normal line of the boundary, p−jq (p is when there is no energy absorption) Can be expressed as the refractive index of, and q is the extinction coefficient.

From these facts, the complex refractive index n of the medium 2 is
_j2 is obtained from Equation 2.

[0035]

N _j2 ² = (p-jq) ² + n ₁ ² sin ² β ₁ Equation 2

By substituting equation 2 into equation 1, equation 3 is obtained.

[0037]

## EQU3 ## ε = ε ₀ {(p ² −q ² + n ₁ sin β) −j2 (pq)} Equation 3

In equation 3, since ε ₀ , n ₁ and β are known, if the sizes of p and q are known, the complex permittivity ε
Also know the size of.

In the orientation degree evaluation apparatus shown in FIG. 1, irradiation of linearly polarized light on the magnetic recording medium and reception of reflected light from the magnetic recording medium are repeated by changing the incident angle of the linearly polarized light on the magnetic recording medium. , The magnitudes of p and q are calculated from the reflected light intensity of the received reflected light and the incident angle when the reflected light intensity is obtained by using the least square method, and the magnitude of the complex permittivity ε is calculated. There is.

As described above, the orientation degree evaluation apparatus shown in FIG.
The reflected light intensity is measured, and the complex dielectric constant ε of the magnetic recording medium 10 is calculated based on the measured reflected light intensity and the incident angle at that time, and the magnitude of the complex dielectric constant ε depends on the degree of orientation. This is utilized to evaluate the degree of orientation.

Referring to FIG. 1, a magnetic recording medium 10 for evaluating the degree of orientation is placed on a rotatable stage 15.

The semiconductor laser 13 is fixed to one end of the support mechanism 12. The support mechanism 12 is supported rotatably by a predetermined angle in the direction of arrow A _{12 about} a point O where the emitted light Ri of the semiconductor laser 13 reaches the magnetic recording medium 10. By rotating a handle (not shown), the support mechanism 12 moves at an angle according to the amount of rotation of the handle. Therefore, by adjusting the angular position of the support mechanism 12, the incident angle β of the emitted light Ri with respect to the magnetic recording medium 10 also changes. A polarizing plate 14 is arranged substantially in the center of the support mechanism 12. The mounting angle of the polarizing plate 14 is determined so that the light passing through the polarizing plate 14 becomes p-polarized light. Therefore, the semiconductor laser
The outgoing light of 12 becomes p-polarized linearly polarized light by passing through the polarizing plate 14, and the p-polarized linearly polarized light irradiates the surface of the magnetic recording medium 10 and is reflected.

The photodiode 22 is fixed to one end of the support mechanism 21. The support mechanism 21 also has an arrow A around the point O.
It is supported so that it can rotate in a predetermined angle in ₂₁ directions. Support mechanism
21 also rotates a handle (not shown) to move an angle according to the amount of rotation of the handle. When the incident angle β of the emitted light Ri changes, the reflection angle of the reflected light Rr also changes, but the angle of the support mechanism 21 can be changed according to the reflection angle, and the reflected light Rr can be received by the photodiode 22.

The semiconductor laser 13 is a laser controller
Controlled by 11. Under the control of the laser controller 11, the emitted light Ri is emitted from the semiconductor laser 13 and passes through the polarizing plate 14 to be p-polarized. The p-polarized outgoing light is reflected at the point O of the magnetic recording medium 10. Reflected light R
The light r is received by the photodiode 22.

A current I corresponding to the light intensity of the reflected light Rr is output from the photodiode 22 and given to the amplifier circuit 23 to be amplified. The current amplified in the amplifier circuit 23 is given to the voltage conversion circuit 24 and converted into a voltage value according to the input current value. A signal representing the voltage value (reflected light intensity) converted by the voltage conversion circuit 24 is given to the computer device 25.

When such a voltage value measurement process is perpendicular to the surface of the magnetic recording medium 10 and the longitudinal direction of the magnetic recording medium 10 and the emitted light Ri are in the same plane, the stage 15 is
It is repeated by changing the angle β of the incident light in the direction perpendicular to the longitudinal direction of the magnetic recording medium 10 by 90 ° rotation and in the case where the emitted light Ri is in the same plane.

The relationship between the voltage value obtained by changing the incident angle β and the incident angle β is shown in FIG. In FIG. 2, when the longitudinal direction of the magnetic recording medium 10 and the emitted light Ri are in the same plane (longitudinal direction graph), the longitudinal direction of the magnetic recording medium 10 and the perpendicular direction and the emitted light Ri are in the same plane. In the vertical direction (vertical graph) and.

The graph showing the relationship between the incident angle β and the voltage value shown in FIG. 2 is displayed on the display screen of the monitor display device 26 whose display is controlled by the computer device 25 and, if necessary, the plotter device. Printed by 27.

FIG. 3 is a flow chart showing the processing procedure of the orientation degree evaluation in the orientation degree evaluation apparatus shown in FIG.

Referring to FIG. 3, the magnetic recording medium 10 is mounted on the stage 15 so that the longitudinal direction and the emitted light Ri are in the same plane.
Placed on top. In this state, the reflected light intensity is measured while changing the incident angle β (step 31). When the relationship between the incident angle β and the reflected light intensity is obtained, the imaginary part ε _{j0 of} the first complex permittivity ε ₀ is calculated from the incident angle β and the reflected light intensity using the least square method as described later. (Step 32).

Then, the emitted light R is emitted in the direction perpendicular to the longitudinal direction.
The stage 15 on which the magnetic recording medium 10 is placed is rotated 90 degrees so that it is in the same plane as i. In this state, the reflected light intensity is measured while changing the incident angle β (step 33). When the relationship between the incident angle β and the reflected light intensity is obtained, the imaginary part ε _{js of} the second complex permittivity ε _s is calculated from the incident angle β and the reflected light intensity using the least square method (step 34). ).

The imaginary part ε _{j0 of} the first complex dielectric constant ε ₀ and the second
The difference between the complex permittivity ε _{s and} the imaginary part ε _js is calculated, and the degree of orientation of the magnetic recording medium 10 is evaluated based on the magnitude of this difference (step 35). When the difference is large, the anisotropy of the dielectric constant is remarkable between the longitudinal direction of the magnetic recording medium and the direction perpendicular to the longitudinal direction, and it is evaluated that the orientation degree is high as shown in FIG. On the other hand, when the difference is small, the dielectric anisotropy is small in the longitudinal direction of the magnetic recording medium and in the direction perpendicular to the longitudinal direction, and it is evaluated that the degree of orientation is low as shown in FIG. This evaluation may be performed by an operator of the evaluation device by looking at the calculated difference, or may be evaluated by the computer device 25 using a concrete threshold value obtained empirically.

FIG. 4 is a flow chart showing the processing procedure of the reflected light intensity measurement processing, which corresponds to the processing of step 31 and step 33 of FIG.

First, the polarizing plate 14 provided on the support mechanism 12 is set so that the light passing therethrough becomes a p-polarized linearly polarized light (step 41). Subsequently, the support mechanism 12 is adjusted so that the incident angle β is 9 degrees, and the incident angle β is 9 °.
The support mechanism 21 is adjusted so as to be able to receive the reflected light when it is set (step 42).

When the support mechanisms 12 and 21 are adjusted, the semiconductor laser 13 is driven under the control of the laser controller 11, and the emitted light Ri is emitted from the semiconductor laser 13.
The emitted light Ri becomes p-polarized linearly polarized light on the polarizing plate 14 and enters the magnetic recording medium 10. The emitted light Ri is reflected by the magnetic recording medium 10, and the reflected light Rr is reflected by the photodiode.
Received at 22. Thereby, the reflected light intensity is measured.

Until the incident angle β reaches 81 degrees, the incident angle β
Is increased by 4.5 degrees and the measurement of the reflected light intensity is repeated (NO in step 44, step 45). The support mechanism 21 receives the reflected light Rr as the incident angle β changes.
Needless to say to move. When the incident angle β becomes 81 ° (YES in step 44), the reflected light intensity measurement process ends.

Such reflected light intensity measurement processing is performed when the longitudinal direction and the outgoing light Ri are placed on the same plane, and when the direction perpendicular to the longitudinal direction and the outgoing light Ri are placed on the same plane. ， Performed for each.

FIG. 5 shows the complex permittivity ε with the imaginary parts ε _j0 and ε _js.
4 is a flow chart showing the processing procedure of the calculation processing of FIG. 3 and corresponds to the processing of step 32 and step 34 of FIG.

From the relationship between the plurality of incident angles β and the reflected light intensities obtained in the reflected light intensity measurement processing, the z component p− of the refractive index vector of the magnetic recording medium 10 is used by the least square method.
Coefficients p and q representing jq are calculated (step 51). Referring to Equation 3, the coefficient of the imaginary part of the complex permittivity can be obtained from 2pq. As a result, the coefficient p
And q are calculated, the imaginary part ε of the first complex permittivity
_j0 and the imaginary part ε _{js of} the second complex permittivity are calculated (step 52).

FIG. 6 shows the coefficients p and q using the method of least squares.
6 is a flowchart showing a processing procedure for calculating
This corresponds to the process of step 51 of.

First, the reflected light intensity is measured a plurality of times by changing the incident angle β (step 61). A characteristic curve F (β) representing the relationship between the incident angle β and the reflected light intensity is calculated from the incident angle β and the reflected light intensity obtained by actual measurement (step 62).

The coefficients p and q and the incident angle β are set to appropriate initial values (step 63). Set p,
Substituting q and β into the equation 4, the calculated value Da of the equation 4 is obtained (step 64).

[0063]

[Equation 4]

However, R _p (p, q, β) in the equation 4
Can be obtained from Equation 5, and R _s (p,
q, β) can be obtained from Equation 6.

[0065]

(Equation 5)

[0066]

(Equation 6)

Until the calculated value Da of the equation 4 becomes the minimum value,
The values of p, q, and β are changed, and the calculation of Expression 4 is repeated (NO in step 65, steps 66 and 64). The values of p and q when the calculated value Da of Expression 6 becomes the minimum are determined as the optimum values (step 67).

Using the values of p and q thus determined, the imaginary part ε _j0 of the first complex permittivity and the imaginary part ε _{js of} the second complex permittivity are determined. ε
As described above, the degree of orientation of the magnetic recording medium is determined from the difference between _j0 and ε _js .

In the processing shown in FIGS. 3 to 6, the calculation processing is performed by the computer device 25.

If the surface of the magnetic recording medium 10 is rough, the reflectance will decrease. However, magnetic tapes, magnetic disks, etc. can be regarded as almost flat, and the decrease in reflectance due to surface roughness can be neglected, causing almost no problems.

In the above, the p-polarized light is used for the magnetic recording medium.
Although 10 is irradiated, the s-polarized light may be irradiated to the magnetic recording medium 10. Furthermore, in the above, the degree of orientation is evaluated by comparing the imaginary parts of the complex permittivity, but it is also possible to evaluate the degree of orientation by comparing the real parts. However, as can be seen from Equation 3, the real part depends on the incident angle β, and therefore when the degree of orientation is evaluated using the real part, the incident angle β should be taken into consideration.

Further, in the above description, the p-polarized linearly polarized light is applied to the magnetic recording medium 10. However, random polarized light, not linearly polarized light, is applied to the magnetic recording medium 10, and the first dielectric constant and the second dielectric constant are applied. May be calculated and the degree of orientation may be evaluated. When random polarization is used, the random polarization is divided into a p-polarization component and an s-polarization component, and the first complex permittivity and the second complex permittivity are calculated by applying the formulas 5 and 6. Become.

Further, the magnetic recording medium 10 may be not only a tape-shaped one but also a circular one such as a floppy disk. In this case, perpendicular to the surface of the magnetic recording medium,
In addition, two planes passing through the center and orthogonal to each other are set, and the light beam will be irradiated onto the magnetic recording medium in these two planes.

[Brief description of drawings]

FIG. 1 shows a configuration of a magnetic recording medium orientation degree evaluation apparatus.

FIG. 2 shows the relationship between incident angle and reflected light intensity.

FIG. 3 shows a processing procedure for evaluating the degree of orientation of a magnetic recording medium.

FIG. 4 shows a processing procedure of reflected light intensity measurement processing.

FIG. 5 shows a process of calculating an imaginary part of a complex permittivity.

FIG. 6 shows a processing procedure for determining coefficients p and q of az component of a refractive index vector by the least square method.

FIG. 7 shows a relationship between refraction and reflection when light is incident on the medium 2 from the medium 1.

8 (A) to (C) show polarization states.

FIG. 9 shows a model of moving electrons.

FIG. 10 shows a state of a magnetic recording medium having a low degree of orientation.

FIG. 11 shows a state of a magnetic recording medium having a high degree of orientation.

[Explanation of symbols]

 10 Magnetic recording medium 12, 21 Support mechanism 13 Semiconductor laser 14 Polarizing plate 15 Stage 22 Photodiode 25 Computer equipment

Claims (14)

[Claims] 1. A magnetic recording medium that is an object to be inspected is set with two planes orthogonal to each other and orthogonal to each other, and a light beam is irradiated to the magnetic recording medium in one plane.
Based on the reflected light intensity of the received reflected light and the incident angle when the reflected light intensity is obtained, the reflected light from the magnetic recording medium is received, and the light beam irradiation and the light reception are repeated by changing the incident angle. Then, the first complex permittivity of the magnetic recording medium in the direction parallel to the one plane is calculated, and the optical beam is irradiated to the magnetic recording medium in the other plane of the planes. The reflected light is received, and the light beam irradiation and the light reception are repeated by changing the incident angle. Based on the reflected light intensity of the received reflected light and the incident angle when the reflected light intensity is obtained, A method for evaluating the degree of orientation of a magnetic recording medium, which comprises calculating a second complex dielectric constant of the magnetic recording medium in a direction parallel to a plane. 2. The magnetic recording medium according to claim 1, wherein the larger the difference between the first complex permittivity and the second complex permittivity, the higher the degree of orientation of the magnetic recording medium. Orientation evaluation method. 3. The method for evaluating the degree of orientation of a magnetic recording medium according to claim 1, wherein the one plane is parallel to the longitudinal direction of the magnetic recording medium. 4. The method for evaluating the degree of orientation of a magnetic recording medium according to claim 1, wherein the light beam is linearly polarized light. 5. The method for evaluating the degree of orientation of a magnetic recording medium according to claim 1, wherein the first complex permittivity and the second complex permittivity are calculated by using the least square method. 6. The larger the difference between the coefficient of the imaginary part of the first complex permittivity and the coefficient of the imaginary part of the second complex permittivity, the higher the degree of orientation of the magnetic recording medium is evaluated. The method for evaluating the degree of orientation of a magnetic recording medium according to claim 2. 7. The linearly polarized light is p-polarized light.
7. A method for evaluating the degree of orientation of a magnetic recording medium according to. 8. A first light source which sets two planes orthogonal to the surface of a magnetic recording medium to be inspected and orthogonal to each other, and irradiates the magnetic recording medium with a light beam in one plane, A second light source that irradiates the magnetic recording medium with a light beam in the other plane of the set planes, a light receiving element that receives reflected light from the magnetic recording medium, the first light source, and the second Angle changing means for changing the angle of incidence of the light beam emitted from the light source on the magnetic recording medium, the irradiation of the light beam on the magnetic recording medium from the first light source, and the reception of the reflected light by the light receiving element. In the direction parallel to the one plane based on the respective reflected light intensities and the incident angles at which the reflected light intensities are obtained, which are obtained by changing the incident angle using the incident angle changing means. The first calculation means for calculating the first complex permittivity of the magnetic recording medium, and the irradiation of the light beam from the second light source to the magnetic recording medium and the reception of the reflected light by the light receiving element, are made incident. Of the magnetic recording medium in the direction parallel to the other plane based on the respective reflected light intensities and the incident angles at which the reflected light intensities are obtained, which are obtained by changing the incident angle using the angle changing means. An orientation degree evaluation apparatus for a magnetic recording medium, comprising: a second calculation means for calculating a second complex dielectric constant. 9. An orientation degree evaluation means for evaluating that the greater the difference between the first complex permittivity and the second complex permittivity, the higher the degree of orientation of the magnetic recording medium. 8. A magnetic recording medium orientation degree evaluation apparatus according to item 8. 10. The orientation evaluation apparatus for a magnetic recording medium according to claim 8, wherein the one plane is parallel to a longitudinal direction of the magnetic recording medium. 11. The orientation evaluation apparatus for a magnetic recording medium according to claim 8, wherein the first light source and the second light source emit linearly polarized light. 12. The first calculating means and the second calculating means calculate the first complex permittivity and the second complex permittivity using a least square method.
The orientation evaluation apparatus for a magnetic recording medium according to claim 8. 13. The orientation of the magnetic recording medium increases as the difference between the coefficient of the imaginary part of the first complex permittivity and the coefficient of the imaginary part of the second complex permittivity increases. 10. The orientation evaluation apparatus for a magnetic recording medium according to claim 9, which is evaluated as having a high degree of orientation. 14. The orientation evaluation apparatus for a magnetic recording medium according to claim 11, wherein the linearly polarized light emitted from the first light source and the second light source is p-polarized light.