JPH0240580A - Observing apparatus of domain - Google Patents

Abstract

PURPOSE:To enable the reliable observation of a domain of a sample made of a material having a small Kerr rotation angle or a Faraday rotation angle, by making rotatable the polarization plane of a polarizer or the light transmission aixs of an analyzer. CONSTITUTION:A linear polarization is applied to a sample 11 at a first position of rotation of a polarizer 4 or an analyzer 17, and a first optical image of a transmitted light or a reflected light subjected to a light-magnetism mutual action in accordance with the state of magnetization of the sample 11, which is obtained after passing through the analyzer 17, is picked up by an image pickup camera 18. Next, a first pickup output is inputted to an image processing device 19 and memorized, and a second optical image having brightness and darkness inverse to ones of the first optical image is obtained at a second position of rotation of the analyzer 17, as an optical image obtained after the light passes through the analyzer 17, and is picked up by the camera 18. Subsequently, a second pickup output is inputted to the image processing device 19 and a difference signal from the input based on the first optical image memorized previously is obtained therein. By casting and reproducing 20 an optical image based on the difference signal, reliable observation of a domain can be performed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an observation device for observing magnetic domains of various magnetic materials including magnetic thin films such as perpendicular magnetic recording media and perpendicular magnetization films of magneto-optical recording media. Involved.

[Summary of the invention]

The present invention irradiates a magnetic domain observation sample with linearly polarized light, and uses optical-magnetic interaction and image processing in the magnetic domain observation sample to directly observe the magnetization state of the sample, that is, the magnetic domains, using a monitor image projection device. In particular, by rotating the polarizer or analyzer, we obtain two types of optical images in which the brightness and darkness of the observed magnetic domain are reversed, and by capturing these images and performing high-speed image processing, we can observe the magnetic domains in real time as clear images with less noise. To provide a magnetic domain observation device capable of direct observation in so-called real time.

[Conventional technology]

Development of magnetic materials such as various magnetic thin films and permanent magnets, ri7F
Observation of magnetic domains is important in research. For example, in order to analyze the recording state of perpendicular magnetic recording media or noise in magneto-optical recording media, it is possible to accurately and easily observe the magnetic domain state of the perpendicular magnetization itself or the state of magnetic domain generation as recorded information bits. There is a high demand for being able to do this. In recent years, perpendicular magnetic domain observation devices using the polar Kerr effect and image processing have been developed for magnetic domain observation (for example, the IE Transactions on Magnetics (The Institute of Magnetics)
electricand electronics E
ngineers Transactions onM
agneLics) Vol, M to G-21, (
1985) PP1596-159B.

and the same magazine νo1. MAG-23, (1987) PP2
067-2069).

[Problem to be solved by the invention]

When performing magnetic domain observation using such a polar Kerr effect, relatively clear images can be obtained if the material to be observed has a large Kerr rotation angle, but if the Kerr rotation angle is small, a relatively clear image can be obtained. When it comes to things, especially Ken IS! If the bank ground noise caused by marks or the like is relatively large, there is a problem that an observation image cannot be obtained at all or a clear observation image cannot be obtained.

The present invention provides a magnetic domain observation device designed to solve these problems.

[Means to solve the problem]

As shown in FIG. 1, the present invention provides a linearly polarized light source section (11
, a magnetic domain observation sample placement section (12), an analyzer (17), an imaging camera (18), an image processing device (19), and a monitor image projection device (20), The polarization plane of the polarizer (4) or the light passing axis of the analyzer (17) in the light source section (L) is at least 1O.

Allowed to rotate. Then, at the first rotational position of the polarizer (4) or analyzer (17), the magnetic domain observation sample is irradiated with linearly polarized light, and the magnetic domain observation sample undergoes optical-magnetic interaction according to the magnetization state. A first optical image after passing through the transmitted light or reflected light analyzer (17) is captured by an imaging camera (18), and this first imaging output is input to an image processing device (19). Memorize this and
At a second rotational position of the analyzer (17), a second optical image whose brightness and darkness are reversed from that of the first optical image is obtained as an optical image after passing through the analyzer (17), and this second optical image is captured. Camera (18)
This second imaging output is sent to an image processing device (
19) to obtain a difference signal from the input based on the first optical image previously stored in memory, and the optical image based on this signal is projected and reproduced on the image projection device (20) to observe magnetic domains. conduct.

[Effect]

According to the above-described apparatus of the present invention, it is possible to observe the magnetic domains of a sample having information bits formed by magnetic domains recorded by a magnetic head in a perpendicular magnetic recording medium, or a sample having information bits formed by magneto-optical recording, that is, by bubble magnetic domains, for example. It can be performed. In this magnetic domain observation, first, the polarizer (4) and the analyzer (17) are set in a crossed Nicol state so that the light passing axes of solid lines a and b are shown in FIG. In this state, for example, the light passing axis of the analyzer (17) is rotated, for example, by +θ as shown by the chain line C. In this way, the light of the vibration component in the solid line C direction of the reflected light rotated ±θ due to the Kerr effect corresponding to the downward and upward magnetization shown by broken lines d and e in the sample (11) is transmitted to the analyzer (1
7) and is detected. In other words, light rotated by 10X due to downward magnetization is more likely to be blocked, and the solid line C for light rotated by 10X due to upward magnetization.
A first optical image, for example, as shown in FIG. 3A, in which the directional component passes through more easily, is obtained, and this is captured by the imaging camera (18) and stored in the image processing device (19). Next, the light passing axis of the analyzer (17) is rotated by -θ as shown by the chain line f. In this case, contrary to the previous case, the light rotated by 1θ due to upward magnetization is more likely to be blocked, and the component in the direction of the solid line C of light rotated ±θ due to downward magnetization is more likely to pass through. As shown in Figure 3B, Figure 3A
A second optical image whose brightness and darkness are reversed from that of the first optical image is obtained. This second optical image is captured by an imaging camera (18), and the first optical image is subtracted by an image processing device (19). In this way, as shown in FIG. 3C, most of the noise components are eliminated and an output with a high signal level is obtained.
), it is possible to project a bright and clear image of the magnetic domain.

Here, θ can be selected to be equal to the Kerr rotation angle θ, but it is preferable to set 1 so that 1θ1>1θ. For example, when the Kerr rotation angle of magneto-optical disk material TbFe or GdTbFc yarn is; θK l = 0.1 to 0.4°, θ
It is desirable to set I=■°, and the reason for doing so is that the human eye's ability to distinguish between brightness and darkness is better and better when the entire screen is bright to a certain extent. Also, for this reason, when the analyzer is rotated 20 = 14 degrees, the lens barrel (35
) must be fixed and adjusted so that the rotation is less than 0.1°. Otherwise, high-resolution magnetic domain observation is impossible.

In addition, in the above explanation, by rotating the analyzer (17),
In the case where the first and second optical images were obtained, the polarizer (4
) can also be rotated so that the analyzer (17
) and the polarizer (4) can be rotated relative to each other to obtain the first and second optical images.

〔Example〕

The linearly polarized light source section (1) is, for example, as shown in FIG.
It comprises a light source (1) such as a 100 W ultra-high pressure mercury lamp, a Koehler lens (3), and a polarizer (4), for example, a calcite Glan-Thompson prism with an extinction ratio of 10-5 or more.

(5) is a light source! 11 shows a starting power source for an ultra-high pressure mercury lamp.

The external magnetic field applying means (16) has a stationary configuration, as shown in FIG. 4 as a plan view, and as shown in FIG. 5 as a sectional view taken along line A--A in FIG. 4. That is, they each have a high permeability center ball (13) and a straight core (15).

In the figure of the center ball (13), the straight core (15) has a bottom plate part (15A) that is magnetically tightly coupled or integrated with the lower end of the center ball (13), and a bottom plate part (15A) that is concentric with the center ball (13) from its outer periphery. The peripheral wall portion (15B) is arranged to extend upwardly, and the top plate portion (15C) is magnetically closely coupled to the upper end of the circumferential wall portion (15B) and is arranged to face the bottom plate portion (15A). It consists of A through hole (15h) is bored in the center of the top plate (15C), and a center ball (15h) is formed in the center of the top plate (15C).
3), there is a center hole (
21a), for example, a disc-shaped SUS of non-magnetic metal.
A non-magnetic plate (21) made of 304 is inserted and crimped.

In FIG. 1, (30) indicates an excitation power source for the external magnetic field applying means (16). Fluctuations in the magnetic field due to fluctuations in the current flowing to the wire ring (14) of the external magnetic field applying means (16), etc.
When observing submicron-order magnetic domains, it is desirable to suppress the amount to 3% or less.

This external magnetic field applying means (16) has, for example, a straight core with a radius of 73 mm and a non-magnetic plate (21) with a radius of 25 mm.
When the voltage applied to the coil (14) is 0.21V, the generated magnetic field is 4 KOe, and when it is 0.43V, it is 6.5.
K.O.E.

You can get Oe at 9 when it is IV.

Furthermore, it is desirable that the external magnetic field applying means (16) be cooled by air cooling in order to avoid thermal effects on the sample (11) and the optical system even when used continuously for a long time.

The upper end of the center pole (13) is preferably formed into a conical shape, and the Vertier element (22) is disposed at this conical end.

As shown in FIG. 5, this Beltier element (22) has, for example, a cylindrical through hole (22a>) into which the conical upper end of the center pole (13) is inserted, and is arranged oppositely. It is possible to adopt a configuration in which electric lights (23□) and (232) are arranged on both main surfaces, with one being a cold pole and the other being a hot pole depending on the polarity of the applied voltage.Then, one of the lights tJli (
23t) side as the magnetic domain observation sample arrangement part (12), and the magnetic domain observation sample (11) is placed on this so as to form almost the same surface as the upper end surface of the center pole (13).Ii!
Make sure that the equipment is installed.

Then, the side of the Vertier element (22) opposite to the sample placement section (12) is thermally connected to the center pole (13).

On the other hand, the fixing means (24) for fixing the magnetic domain observation sample (11)
) will be established. This fixing means (24) includes, for example, a pair of non-magnetic and low thermally conductive holding arms (24) made of aluminum, for example.
25t) and (252). Each holding arm (251
) and (252), for example, each outer end thereof has a straight core (
15) Screws (261) and (2
62), with each inner end abutting on the side edge of the sample (11), to place the sample (11) in the sample positioning section (12).
That is, in this example, it is pressed and held toward the Vertier element (22) and further toward the upper end surface of the center pole (13).

In addition, as shown in FIG. 4, in the sample placement section (12), for example, a temperature detection element (27) such as a thermocouple of a digital thermometer (26) is placed as close as possible to or in contact with the magnetic domain observation sample (11). do. And a digital thermometer (26
) is input to the digital controller (28), and the output from the Bertier element (22) is input to the electric circuit (231) and (23x).
The voltage and polarity applied to the sample mounting section (12) are controlled to control the temperature of the sample mounting section (12). This Bertier element (22
), sample (11) (7) M-placement part (12) (7
) The temperature can be variably controlled in the range of -15°C to +80°C.

On the other hand, as shown in Fig. 1, the magnetic domain observation sample arrangement section (12
) is provided with a polarizing microscope (29).

The analyzer (17) may be constituted by an analyzer in the intermediate tube of this polarizing microscope (29).

(31) is an objective lens, and this objective lens (31) is
For example, a lens with a magnification of 80x, 100x, etc. can be used, but its aperture @N, A is relatively small, 0.8, for example, Nikon Ultra Long Working Distance Plan Acroart CFMP Lan.
ELInD (product name) can be used. In addition, the objective lens (31) is N with a magnification of 100 times as described above.
, A, = 0.8, and a glass correction ring (0,9
A lens with a refractive index correction of glass with a thickness of 1.5 mm to 1.5 mm is used.

(32) indicates a reflective lighting device.

The imaging camera (18) may be, for example, a CCD solid-state imaging camera with a magnification of 17 times.

The image processing device (19) has a resolution of 640 x 480
It can be a high-speed image processing device with x60 bits, arithmetic functions, and a maximum integration of 256 frames.

The monitor image display device (20) may be configured with a cathode ray tube type television picture tube.

A video printer (33) is also provided, so that the image projected by the image projection device (20) can be printed as a so-called hard copy if necessary.

A light source section (1) of a magnetic domain observation device having the above-described configuration.

The external magnetic field applying means (16), the polarizing microscope (29) including the analyzer (17), the imaging camera (18), etc. are arranged on the vibration isolation table (34) while maintaining a predetermined positional relationship with each other.

An example of magnetic domain observation using the above-described apparatus of the present invention will be explained.

Observation Example 1 In this case, as shown in FIG. GdT of
There is a magneto-optical disk having a structure in which a bFe-based magnetic thin film (43) is deposited, and a silicon-based protective film (44) with a thickness of 1,500 mm is further deposited on top of this. Magnetic domains are formed, and this is what we are trying to observe.

In this case, the objective lens (31) has a magnification of 100x.

N, A, = 0.8 was used.

The observation was performed using the light source section (1) without applying an external magnetic field.
irradiated with polarized light from the protective film (44), and the magnetic domains were observed using the procedure explained in FIGS. 2 and 3. In this case, we were able to clearly observe the magnetic domains.

Observation Example 2 A glass substrate (birefringence double bus of 10 nm) was used as the substrate (41) of the magneto-optical disk, a signal was recorded, and the recorded information bits were observed using the same method as Observation Example 2. This was done from the substrate (4) side. Also, in this case, the objective lens (31) has a magnification of 40x, N, A, = 0.5,
A lens having a correction ring for correcting the refractive index of glass having a thickness of θ˜21 was used. In this case, we were able to clearly observe the magnetic domains.

Comparative Example 1 A polycarbonate substrate (birefringence double bus exceeds 20 nm) was used as the substrate (41) of the magneto-optical disk,
The signal was recorded and the recorded information bits were recorded in the same manner as in Observation Example 4. In this case, the observed image was so distorted that image processing magnetic domain observation could not be performed.

Observation Example 3 The same sample (11) as in Observation Example 1 was subjected to magnetic domain observation from the substrate (41) side using the same method, but in this observation example, the objective lens (31) was
0 times, N, Δ, = 0.8, glass correction ring (0.9 m
A lens with a thickness of m = 1.5 mm (correcting the refractive index of glass) was used. Clear observations were made in this case as well.

Comparative Example 2 As the objective lens (31), a lens with a magnification of 100 times and N=0.9 was used.
Observations similar to those in Observation Example 2 were conducted using the following. In this case, observation of magnetic domains was unclear.

When N, A, is 0.9 as in Comparative Example 2, the observed image becomes unclear, but when N, A, = 0.8 as in Observation Examples 2 and 3, the magnification is 100. Clear magnetic domain observation is now possible with a 2x objective lens.

This is due to linearly polarized light, which is greatly affected by lens distortion, but with a lens of N, A, = 0.8, distortion is less likely to occur. However, N3^, = 0.8 is sufficient to hinder observation, so there is no need to use a device with λ N,A of less than 0.8.

In observation example 1 described above, the magnetic domain was observed from the side opposite to the substrate (41), but in a general magneto-optical disk, the magnetic domain is observed from the side opposite to the base (41) of the magnetic thin film (43). A reflective film such as Δ1 reflection is provided on the side, and the base 1 (41
) side, and it is desirable to observe from the base It(41) side in magnetic domain observation as well. In this case, the substrate (41) is a group F.
In order to prevent magnetic domain observation from being obstructed by birefringence in i(41), it is made of a material with small birefringence, specifically, a double bus of 20 nm or less, such as a glass substrate.

Observation Example 4 A recording signal with a wavelength of 10 μm was applied to a mounted magnetic recording medium on which a Co-Cr magnetic film with a thickness of 0.2 μm was deposited on a surface molecular film by DC magnetron sputtering, and the trunk width was measured by a fixed magnetic head. Magnetic recording was performed at 26 μm. This magnetic recording medium was irradiated with polarized light from the light source section (11) from the Co-Cr vL film side without applying an external magnetic field.
N was removed to observe the magnetic domains. In this case, the objective lens (31) had a magnification of 100 and N,^,=0.8.

In this case, we were able to clearly observe the magnetic domains.

Comparative Example 3 The analyzer (17) was fixed at the first rotational position for the sample in Observation Example 4, and no image processing was performed. In this case, no magnetic domains could be observed. This is Co-C
This is because the Kerr rotation angle of the r-magnetic film is too small, resulting in a small difference in brightness and the human eye being unable to distinguish the inverted portions of the magnetic domains.

In the above example, magnetic domains are observed using reflected light from the sample (11), that is, Kerr rotation, but similar magnetic domain observation can be performed using transmitted light, that is, Faraday rotation. You can also do it.

Furthermore, in the above example, the external magnetic field applying means (16) can select the externally applied magnetic field to the sample (11), and the Vertier element (22) can set the temperature of the sample (11). Observation of each magnetic domain can be performed under desired external magnetic field application and temperature.

〔Effect of the invention〕

As described above, according to the apparatus of the present invention, it is possible to reliably eliminate bank ground noise, and accordingly, for the sample (11) made of a material with a small Kerr rotation angle or Faraday rotation angle, It is also possible to perform reliable magnetic domain observation, and its practical benefits are extremely large.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of an example of the device of the present invention, Fig. 2 is an explanatory diagram of the principle of magnetic domain observation, Fig. 3 A-C is an explanatory diagram of captured optical images in an example of magnetic domain observation, and Fig. 4 is an illustration of magnetic field application. A top view of the means, FIG. 5 is a cross-sectional view taken along line A-A in FIG. 4, FIG. 6 is a cross-sectional view of an example of a portion where a Vertier element is arranged, and FIG. 7 is a cross-sectional view of an example of a magnetic domain observation sample. . (1) is a linearly polarized light source section, (2) is a light source, (4) is a polarizer, (11) is a magnetic domain observation sample, (12) is a magnetic domain observation sample placement section, (13) is a center ball, (14) is a wire ring,
(15) is a stationary core, (16) is an external magnetic field applying means, (
17) is an analyzer, (18) is an imaging camera, (19) is an image processing device, and (20) is a monitor image projection device.

Claims (1)

[Claims] 1. A linearly polarized light source section, a magnetic domain observation sample arrangement section, an analyzer, an imaging camera, an image processing device, and a monitor image projection device, the analyzer comprising: The light passing axis is rotatable, and at the first rotational position of the analyzer, the linearly polarized light from the light source section is irradiated onto the magnetic domain observation sample, and the light A first optical image of the transmitted light or reflected light that has undergone magnetic interaction after passing through the analyzer is captured by the imaging camera, and the first imaging output is input to the image processing device. is stored in memory, and at a second rotational position of the analyzer, a second optical image whose brightness and darkness are reversed from that of the first optical image is obtained as an optical image after passing through the analyzer, and the second optical image is obtained. imaged by the above-mentioned imaging camera,
The second imaging output is input to the image processing device to obtain a difference signal from the input based on the first optical image stored in the memory, and an optical image based on the signal is displayed on the image projection device. A magnetic domain observation device characterized in that magnetic domain observation is performed by performing magnetic domain observation. 2. Equipped with a linearly polarized light source section having a polarizer, a magnetic domain observation sample placement section, an analyzer, an imaging camera, an image processing device, and a monitor image projection device, and the polarizer The transmission axis is rotatable, and at the first rotational position of the polarizer, linearly polarized light is irradiated onto the magnetic domain observation sample, and the transmitted light undergoes optical-magnetic interaction according to the magnetization state of the magnetic domain observation sample. A first optical image of the light or reflected light after passing through the analyzer is captured by the imaging camera, the first imaging output is input to the image processing device to store it in memory, and the polarizer is Obtaining a second optical image whose brightness and darkness are reversed from the first optical image at a second rotational position as an optical image after passing through the analyzer, and capturing the second optical image with the imaging camera; The second imaging output is input to the image processing device to obtain a difference signal from the input based on the first optical image stored in the memory, and an optical image based on the signal is displayed on the image projection device. A magnetic domain observation device characterized in that magnetic domain observation is performed by performing magnetic domain observation.