JPH11231031A - Magnetic domain observing method and magnetic domain observation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To observe a micro magnetic domain by scanning the surface of a magnetic material by a Hall element with resolution in a specific range while applying the magnetic field on the magnetic material. SOLUTION: In a Hall element, a semiconductor pattern formed of GaAs/ AlGaAs heterojunction is formed on a material. An intersecting area of a current line 2 of the semiconductor pattern and a voltage detection line orthogonal to the current line 2 becomes a magnetic field detecting part which is kept within a range of about 2 μm×2 μm. The resolution of the Hall element is therefore about 2 μm×2 μm or less. In the case of the surface of a magnetic material not having enough conductivity, a conductive thin film of Au or the like is formed on the surface of the magnetic material. A probe 4 of STM is formed on the surface of the substrate near the magnetic field detecting part. A magnetic domain observation device is composed of this Hall element, a magnetic field applying means, and a temperature control means added, if necessary. The change of magnetic domain structure consequent to the magnetic field fluctuation of the magnetic material surface can therefore be observed at real time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic domain observing method capable of observing a magnetic domain structure on a magnetic material surface in a strong magnetic field, and a magnetic domain observing apparatus used in the method.

[0002]

2. Description of the Related Art The magnetic domain structure of a magnetic material can be known from the structure of magnetic domains existing on the surface of the magnetic material. In order to investigate the properties of the magnetic material in detail, it is important to know the change in the magnetic domain structure due to the magnetic field. For example, in order to investigate the mechanism of magnetization reversal of a sintered ferrite magnet, it is necessary to know the growth of reverse magnetic domains and the rotation of magnetization. By comparing the magnetic domain structure before and after applying a magnetic field, it is possible to estimate the reverse domain growth and magnetization rotation.However, in order to obtain more accurate information, the change in the magnetic domain structure due to the change in the magnetic field strength must be determined. It is preferable to check in real time. However, no proposal has been made so far for examining a structural change of a minute magnetic domain such as a magnetic domain of a sintered ferrite magnet in a magnetic field.

Conventionally, for domain observation, a bitter method, a magneto-optical microscope, an electron beam, a magnetic force microscope, and the like have been used.
However, the bitter method and the magneto-optical microscope have insufficient resolution for observing minute magnetic domains. Also, in electron beam observation, the magnetic field affects the electron beam,
Difficult to use in a magnetic field. Further, in a magnetic force microscope, it is necessary to scan a probe made of a magnetic material, and since the probe is affected by a magnetic field, it is difficult to use the probe in a magnetic field.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to enable observation of minute magnetic domains existing on the surface of a magnetic material in a strong magnetic field.

[0005]

This and other objects are achieved by any one of the following constitutions (1) to (7). (1) Resolution is 2 μm while applying a magnetic field to a magnetic material
A magnetic domain observation method for observing the structure of magnetic domains on the surface of the magnetic material by scanning the surface of the magnetic material with a Hall element having a size of × 2 μm or less. (2) The magnetic domain observation method according to the above (1), wherein the intensity of the magnetic field is 0.1 T or more. (3) The magnetic domain observation method according to the above (1) or (2), wherein the magnetic domain is observed while controlling the temperature of the magnetic body. (4) The magnetic domain observation method according to any one of (1) to (3), wherein the magnetic domain is observed while maintaining a constant distance between the surface of the magnetic body and the magnetic field detection unit of the Hall element. (5) Any of the above (1) to (4), wherein a probe of a scanning probe microscope is formed in the vicinity of the magnetic field detecting section of the Hall element, and the surface shape of the magnetic body is observed simultaneously with the observation of the magnetic domains. How to observe the magnetic domain. (6) A magnetic domain observation device including a Hall element having a resolution of 2 μm × 2 μm or less and a magnetic field applying unit. (7) The magnetic domain observation device according to (6), further comprising a temperature control means.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a Hall element having a very small size of a magnetic field detecting section is used in order to increase the spatial resolution in observing a magnetic domain. The Hall element can observe magnetic domains without being affected by a magnetic field even in a strong magnetic field, for example, a magnetic field of 1 T or more. Further, since the Hall element can accurately measure the intensity of the external magnetic field applied to the magnetic body, the magnetic flux density distribution on the surface of the magnetic body can be accurately known. Therefore, according to the present invention, it is possible to examine the structure of the minute magnetic domains on the surface of the magnetic body in a strong magnetic field, and to dynamically know the change of the magnetic domains due to the fluctuation of the magnetic field.
Also, if you observe the magnetic domains while controlling the temperature of the magnetic material,
It is possible to dynamically know the change of the magnetic domain due to the temperature change.
The strength of the applied magnetic field may be appropriately determined according to the type of the magnetic substance to be observed, but is usually 0.1 T or more. The upper limit of the applied magnetic field strength is not particularly limited, but is usually about 10T.

In order to accurately measure the magnetic flux density distribution on the surface of the magnetic material, it is necessary to keep the magnetic field detector of the Hall element at a fixed distance from the surface of the magnetic material. As a means for this,
For example, a scanning probe microscope such as a scanning tunnel microscope (STM) and an atomic force microscope (AFM) can be used. If a Hall element provided with a probe of a scanning probe microscope near the magnetic field detecting unit is used, a surface image can be obtained at the same time as obtaining a magnetic domain image of a magnetic body.

FIG. 1 is a trace diagram of a scanning electron microscope photograph showing a main part of a configuration example of a Hall element used in the present invention. This Hall element has GaAs / AlGa on a substrate.
A semiconductor pattern composed of an As hetero junction is formed. This semiconductor pattern includes a current line 2 and a voltage detection line 3 orthogonal to the current line 2, and a region where the two intersect is a magnetic field detection unit. An STM probe 4 is formed on the surface of the substrate near the magnetic field detecting section. This probe is formed by forming an Au film on the heterojunction by vapor deposition, irradiating the Au film with an electron beam to precipitate carbon contained as an impurity. The Hall element with this structure is described in the 43rd Annual Meeting of the Japan Society of Applied Physics, p.441.

According to the present invention, the magnetic field detector of the Hall element
The dimensions should be within the range of 2 μm × 2 μm. The resolution of the Hall element is about the same as the size of the magnetic field detection unit.

When the surface observation by the STM is performed at the same time as the magnetic domain observation, the surface of the magnetic material needs to be conductive. If the magnetic material surface does not have sufficient conductivity, a conductive thin film made of Au or the like may be formed on the magnetic material surface.

The magnetic domain observation device of the present invention has a Hall element having the above resolution, a magnetic field applying means, and further has a temperature control means as required. The configuration of the magnetic field applying means is not particularly limited, and is preferably configured using a permanent magnet, an electromagnet, or the like so that the intensity of the applied magnetic field can be changed. Also,
If a temperature control unit having a heater and / or a cooler is provided, it becomes possible to observe a magnetic domain change accompanying a temperature change in real time.

The present invention can be used for observing the magnetic domain structure of various magnetic materials. Preferred examples of the magnetic substance to be observed include an oxide magnetic material such as a ferrite sintered magnet and a ferrite soft magnetic material, a metal magnetic material, and an organic magnetic material.

[0013]

EXAMPLE A Hall element having the structure shown in FIG. 1 was manufactured. This Hall element is made of GaAs / AlGaAs as described above.
It has a semiconductor pattern composed of an s heterojunction and has an STM probe provided near a magnetic field detection unit. The dimensions of the magnetic field detector were 0.5 μm × 0.5 μm.

Using this Hall element, a magnetic domain image on the surface of the sintered ferrite magnet was observed. Prior to this observation, an Au thin film having a thickness of 100 nm was formed on the surface of the sintered ferrite magnet. FIGS. 2 and 3 show magnetic domain images by the Hall element when no magnetic field is applied and when a magnetic field of 0.2 T is applied in a direction perpendicular to the plane of the paper, respectively. FIGS. 2 and 3 show a region having a side of 50 μm. This ferrite sintered magnet has an average crystal grain size of about 10 μm.

A comparison between FIG. 2 and FIG. 3 shows that the state of the magnetic domains is significantly different. That is, according to the present invention,
It can be seen that a change in the magnetic domain structure of the magnetic material when a magnetic field is applied is clearly captured.

[0016]

According to the present invention, it is possible to know in real time a change in the magnetic domain structure on the surface of the magnetic material due to a change in the applied magnetic field.

[Brief description of the drawings]

FIG. 1 is a trace diagram of a scanning electron micrograph showing a main part of a Hall element used in the present invention.

FIG. 2 is a drawing substitute photograph showing a particle structure, and is a magnetic domain image of a surface of a sintered ferrite magnet when a magnetic field is not applied, obtained by a Hall element having a structure shown in FIG.

FIG. 3 is a drawing substitute photograph showing a particle structure, and is a magnetic domain image of a ferrite sintered magnet surface when a magnetic field is applied, obtained by a Hall element having the structure shown in FIG.

[Explanation of symbols]

 2 Current line 3 Voltage detection line 4 Probe

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Jun Nakagawa 1-13-1 Nihonbashi, Chuo-ku, Tokyo Inside TDK Corporation

Claims (7)

[Claims] 1. A magnetic domain observation method for observing the structure of magnetic domains on the surface of a magnetic body by scanning the surface of the magnetic body with a Hall element having a resolution of 2 μm × 2 μm or less while applying a magnetic field to the magnetic body. 2. The magnetic domain observation method according to claim 1, wherein the intensity of the magnetic field is 0.1 T or more. 3. The magnetic domain observation method according to claim 1, wherein the magnetic domains are observed while controlling the temperature of the magnetic body. 4. The magnetic domain observation method according to claim 1, wherein the magnetic domain is observed while keeping a constant distance between the surface of the magnetic body and the magnetic field detection unit of the Hall element. 5. In the vicinity of a magnetic field detecting section of the Hall element,
The magnetic domain observation method according to any one of claims 1 to 4, wherein a probe of a scanning probe microscope is formed, and the surface shape of the magnetic body is observed simultaneously with the magnetic domain observation. 6. A magnetic domain observation device comprising a Hall element having a resolution of 2 μm × 2 μm or less and a magnetic field applying means. 7. The magnetic domain observation device according to claim 6, further comprising temperature control means.