JPH03274481A - Device for detecting magnetic information - Google Patents

Abstract

PURPOSE:To enable detection of information on the magnetic force of the surface of a sample and information on the surface shape thereof with high sensitivity and high resolution by providing a magnetic probe with a coil for controlling the magnitude of magnetization of the probe and the orientation of magnetization. CONSTITUTION:A cantilever 1, a support 2 constructed integrally therewith and a hole 3 are provided. The fore end part 4 of the cantilever 1 is machined to have a sharply pointed shape by a technique of photolithography. Next, a magnetic probe 5 is provided on the surface of the cantilever 1 and a coil 6 is provided at on end of the probe 5 so as to control the magnitude of magnetization thereof. When the probe 5 approaches the surface of a magnetic sample, a magnetic force acts between them and the cantilever 1 is subjected to deflection by this force. The amount of this deflection depends also on the magnitude of magnetization of the probe 5 in addition to the strength of the magnetic field of the sample. Accordingly, the magnitude of magnetization of the probe 5 is so controlled as to keep the amount of deflection of the cantilever 1 fixed, by varying a current made to flow through the coil or the direction of the current. By monitoring the value of a signal of this control, information on the magnetic force between the magnetic sample and the probe 5 can be obtained.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention utilizes magnetic force or tunneling current generated when a magnetic probe and a sample such as a magnetic material are brought close to each other to determine the surface morphology or shape of the sample. Scanning magnetic force microscope, scanning tunneling microscope, or atomic force microscope to obtain information on magnetic properties
This invention relates to magnetic information detection devices such as lj mirrors.

[Conventional technology 1] A scanning tunneling microscope, which is a conventional technology, applies a voltage between the probe and the sample, and utilizes the tunneling current and field emission current obtained when the probe and the sample are brought close together. This is a device that examines the surface morphology of a sample. On the other hand, a scanning magnetic force microscope is a device that uses a magnetic material as a probe and uses the magnetic force when the magnetic probe approaches a magnetic sample to investigate the magnetization state of the sample.

Conventionally, a scanning magnetic force microscope 1!3! utilizes the magnetic force obtained by bringing a magnetic probe and sample close together. For information on how to obtain magnetic information about a sample using a mirror, see Journal of Vacuum Science Technology^6 (1988), pp. 279 to 282, or Applied Physics Letters, Vol. 50 (1987), No. 145.
Discussed on pages 5 to 1457.

Regarding probes that detect the atomic force generated when a sample and probe are brought close, see European Physics Letter 3 (1987), pp. 1281 to 128.
Page 6 (Europhys, Lett, 3 (1,9
87) pp 1281-1286).

Problem 1 to be Solved by the Invention A magnetic force microscope is a device that detects the magnetic force generated by the interaction between a leakage magnetic field on the surface of a magnetic sample and a magnetic probe.

The magnetic probe used in the above-mentioned prior art has a configuration in which the tip of a magnetic wire made of nickel (N1) or iron (Fe) is bent into an L-shape. Ni and Fe have high saturation magnetic flux density and 8O
It is a material with a small coercive force of A/m or less. In this case, when a magnetic probe made of Nl or Fe approaches the surface of a magnetic sample using the conventional technique, the magnitude and direction of magnetization of the magnetic probe change due to the leakage magnetic field from the surface of the magnetic sample.

The drawback was that it was not possible to obtain high-sensitivity, high-resolution magnetic lunar information.

In addition, with conventional technology, errors occur due to changes in the gap between the probe and the sample, so the measured magnetic force (including surface morphology information)
Even if surface morphology information is removed from the surface, accurate magnetic lunar information cannot be obtained, and accurate magnetic lunar information and surface morphology information cannot be separated.

An object of the present invention is to provide a magnetic information detection device that can detect magnetic moon information and surface morphology information on a sample surface with high sensitivity and high resolution.

[Means for Solving the Problems] In order to achieve the above object, a coil for controlling the magnitude and direction of magnetization of the magnetic probe was installed in the i-probe.

[Operation] A coil is installed around the magnetic probe, and the magnitude of magnetization at the tip of the magnetic probe is controlled by changing the value of the current flowing through the coil. Furthermore, by changing the direction of the current flowing through the coil, the direction of magnetization at the tip of the magnetic probe is changed. The magnetic probe with this configuration operates as follows, for example. When a magnetic probe with a magnetized tip approaches the surface of a magnetic sample, a magnetic force acts between them, and the cantilever is deflected by this force. The amount of this deflection depends not only on the strength of the sample's magnetic field but also on the magnitude of the magnetization of the magnetic probe.

Therefore, the magnitude of magnetization of the magnetic probe is controlled by changing the current flowing through the coil and the direction of the current so as to keep the amount of deflection of the cantilever constant.

By monitoring the value of this control signal, magnetic moon information between the magnetic sample and the magnetic probe can be obtained. The amount of deflection of the cantilever can be measured by means of displacement inspection means (for example, tunneling current) provided behind the cantilever.

Alternatively, it can be detected by an optical method (or a change in capacitance), or by measuring the tunneling current between the sample and the magnetic probe.

Furthermore, in the present invention, the magnetization strength of the magnetic probe can be easily controlled by the current flowing through the coil, so it is possible to set the magnetization strength of the magnetic probe so as not to be affected by the leakage magnetic field on the sample surface. It's easy.

Therefore, by separately measuring surface morphology information,
Accurate magnetic moon information can be obtained. Namely.

It is possible to separate and detect the surface morphology information and magnetic moon information of the sample. Surface morphology information can be obtained by passing a high-frequency current through a coil to reduce the maximum magnetization strength of the magnetic probe, that is, lowering the sensitivity to magnetism, and measuring the atomic force of the sample.

A magnetic probe is formed on the surface of a cantilever with a sharp tip. What is the material that makes up the cantilever?

It is desirable to have high rigidity and a large natural frequency.

The cantilever is made of silicon oxide, silicon nitride, diamond-like carbon, etc. or N] or Fe.

It may also be composed of W or the like. It is desirable that the magnetic probe has a small coercive force, preferably 80 A/m or less. Furthermore, in order to improve the frequency response characteristics to magnetization changes, the magnetic permeability of the magnetic material constituting the magnetic probe is set to 1000 or more.

The magnetic probe is made of a magnetic thin film, the axis of easy magnetization of the magnetic thin film is perpendicular or parallel to the surface of the cantilever, and the tip of the cantilever is installed perpendicular to the sample surface. The axis of easy magnetization can be set perpendicular or parallel to the sample surface, making it possible to measure the horizontal or vertical components of the leakage magnetic field on the sample surface with high sensitivity.

Similar measurement means can be applied to a device similar to a scanning tunneling microscope that detects displacement between the sample and the probe due to acoustics, heat, light, etc. in addition to the magnetic force between the sample and the probe.

Further, a coating layer made of a material having lower oxidizing power than the material of the magnetic probe is formed on the surface of the magnetic probe.

Desirable materials for the coating layer include Pt, Pd,
Au.

It is Ru, Rh, Cr, C, and an alloy containing at least one element among these. Further, the desirable thickness of this coating layer is 1100 nm or less. Further, as the material of the covering layer, a material having electrical conductivity is desirable.

More preferably, a non-magnetic material is used.

[Example 1 The present invention will be explained below with reference to Examples.

Example 1 Nine examples will be explained with reference to FIG. A cantilever 1 whose tip is sharply pointed by a photo process and a support body 2 formed integrally with the cantilever. And hole 3 was created. The material for the cantilever 1 is preferably one with high rigidity and low specific gravity. In this example.

A cantilever made of SiO□ formed on a Si substrate was used, but in addition to this, Si, Si3N, W, M
It goes without saying that the same effect can be obtained even if cantilevers 1 having a similar configuration are made using diamond-like carbon or diamond-like carbon. The tip portion 4 of the cantilever 1 was processed into a sharply pointed shape by photolithography technology. The tip portion 4 of the cantilever 1 can be arbitrarily changed, for example, by appropriately selecting the etching rate and etching solution in the photo process. Needless to say, after the photo process, it can be sharpened by processing with ion beam etching or focused ion beam. Next, a magnetic probe 5 was formed on the surface of the cantilever 1. The magnetic probe 5 is.

It was composed of a magnetic thin film and was formed using a vacuum evaporation method. Even when a magnetic material was attached to the surface of the cantilever by a sputtering method or an electric field plating method, a magnetic probe 5 having the same effect could be constructed. The magnetic probe 5 had the axis of easy magnetization of the magnetic thin film parallel to the surface of the cantilever 1, that is, in the direction of the tip of the magnetic probe 5. For this purpose, a magnetic field was applied in the direction that provides the easy axis of magnetization during the formation of the magnetic thin film. Alternatively, a similar effect was obtained by performing heat treatment at 300 to 500° C. in a magnetic field after forming the magnetic thin film. It is desirable that the tip of the magnetic probe 5 is sharply pointed, after the magnetic probe 5 is formed.

It was processed using focused ion beam etching to sharpen the tip with a curvature of less than 1000 Å. It goes without saying that the tip can be sharpened to a curvature of 1000 Å or less by processing by chemical polishing or the like. Magnetic probe 5
80at%Ni-Fe was used as the constituent material. Similar effects can be obtained with permalloy including 80 at% Ni-Fe and Ni, Fe, Co,
Ta.

Zr, amorphous alloy containing Hf, Fe-C based material,
Alternatively, it goes without saying that a multilayer film containing these may be used. The coercive force of the magnetic thin film constituting the magnetic probe 5 was set to 80 A/m or less. In order to control the magnitude of magnetization of the magnetic probe 5, a coil 6 was provided at one end of the magnetic probe 5. By energizing the coil 6, the magnitude and direction of magnetization at the tip of the magnetic probe 5 can be arbitrarily controlled.

Example 2 An example of applying the magnetic probe of the present invention to a magnetic force microscope is shown in the second example.
This will be explained using figures.

Using the magnetic probe prepared as in Example 1, a magnetic force microscope was constructed as shown in FIG.

The tip of the magnetic probe 5 formed on the cantilever 1 was placed in perpendicular contact with the surface of a magnetic sample 6 (a sample in which in-plane magnetic recording was performed on a Co-20 ut% N1 thin film).

That is, the magnetic probe 5 located at the tip of the cantilever 1
The axis of easy magnetization was perpendicular to the sample surface.

In this case, the magnetic probe is made of N], and a PT film is deposited on both sides of the magnetic probe and the cantilever.

A conductive coating film was formed. A metal probe 9 having a sharp tip, such as a W probe 7, was installed behind the cantilever 1. The magnetic sample 6 was placed on a tri-pot 9 made up of three piezoelectric elements 8. By applying a voltage to the piezoelectric element 8, the sample 6 was moved arbitrarily in the Xt, Yt, and Zt force directions. The magnetic probe 5 was magnetized by passing a constant current in a specific direction through a 1° coil so that the tip of the magnetic probe 5 became the south pole. The magnitude and direction of magnetization at the tip of the magnetic probe 5 can be controlled by the value and direction of the current flowing through the coil 1°.

When the magnetic probe 5 approaches the surface of the magnetic sample 6, the magnetic probe 5 receives a force due to the leakage magnetic field on the sample surface, and the cantilever 1
caused a deflection. This deflection is in the direction of repulsion in the region where the magnetic sample is magnetized to the S pole.

On the other hand, the region magnetized to the north pole was displaced in the direction of receiving tension. The amount of deflection of the cantilever 1 is detected as a tunnel current by a W probe 7 installed behind the cantilever 1, and a constant current servo circuit 1 is detected to keep the tunnel current constant.
2 was activated, the sample was moved back and forth by the piezoelectric element 8 in the Z direction of the tripot 9, and the magnetic force to be measured was detected. At the same time, the piezoelectric element was scanned in the X and Y directions by the two-dimensional scanning system 13, and displayed on the display 14 as a magnetic force distribution image on the sample surface. In this measurement system, a constant current is applied to the coil 10 to magnetize the magnetic probe 5, so even if the magnetic probe 5 approaches the sample surface, the magnitude of magnetization at the tip of the magnetic probe remains constant. It was possible to detect accurate magnetic force information with a sensitivity that was about one order of magnitude higher than when the coil 10 was not applied.

In addition to permalloy alloy, ~i,
Fe, Co and alloys containing it, Co-Nb-
Zr.

Similar effects could be obtained using amorphous alloys such as Co--No--Zr and Co--Ta--Zr, or multilayer films of Fe/C and Fe/permalloy.

As a coating layer on the surface of the magnetic probe and cantilever,
In addition to Pt, Ru, Rh, Au, Pd, Cr,
The same effect was obtained even when C and alloys containing it were used.

Example 3 Another application example of the magnetic probe configured as in Example 1 is shown in the third example.
This will be explained using figures.

In this example, the magnetic force was detected by changing the current flowing through the coil 10. That is, when the cantilever 1 is deflected in response to the magnetic force information of the sample, the magnitude of the magnetization of the magnetic probe is changed so that a force is applied to return it to its original state, and the current flowing through the coil 10 at this time is changed. Magnetic force was detected by the amount of change. The control mechanism for the magnitude of magnetization is as follows.

first.

The tip of the magnetic probe 5 is brought close to the magnetic sample 6, and the tunnel current during this time is detected by the current detector 11. Next, keep this tunneling current constant, that is, keep the distance between the sample and the magnetic probe constant.

The value of the current flowing through the coil 10 is controlled by a coil current control circuit 15, and as a result, the magnitude of magnetization of the magnetic probe 5 changes. Furthermore, by scanning the sample in the X and Y directions with the piezoelectric element 8, the magnetization distribution on the sample surface was displayed as an image of changes in the coil current.

Example 4 Another application example of the magnetic probe configured as in Example 1 is shown in the fourth example.
This will be explained using figures.

A nine-probe 7 with a sharp tip was installed behind the cantilever 1, and the tunnel current between these probes was detected by a current detector 11. While keeping this tunneling current constant, the magnetic probe 5. Cantilever 1. and sieve probe 7 to magnetic sample 6.
approached the surface.

The magnetic force was detected based on the change in the current flowing through the coil 10 at this time. The magnitude of the magnetic force between the sample and the magnetic probe 5 depends on the magnitude of magnetization at the tip of the magnetic probe.

The cantilever 1 is displaced in response to this. Magnetic probe 5
The current value applied to the coil 10 is controlled by the coil current control circuit 15 so as to keep the tunnel current between the surface of the cantilever 1 and the shive lobe constant, that is, to keep the distance between the surface of the cantilever 1 and the shive lobe constant. , the magnitude of magnetization at the tip of the magnetic probe 5 is changed. In other words, the magnetic force between the sample surface and the magnetic probe was controlled to be kept constant.

Furthermore, by scanning the sample in the X and Y directions with the piezoelectric element 8, the magnetization distribution on the sample surface was displayed as an image of changes in the coil current.

Example 5 Example 1. Another application example using the magnetic probe and measurement system configured as in Example 2 will be explained with reference to FIG.

The magnetic probe 5 was made of Fe with a coercive force of 80 A/11 or less. In addition to permalloy alloys, Ni, Fe, Co
and alloys containing it, Co-Nb-Zr, Co-
It goes without saying that the same effect can be obtained with a magnetic probe with a coercive force of 8 OA/m or less made of an amorphous alloy such as No-Zr or Co-Ta-Zr, or a multilayer film of Fe/C or Fe/permalloy. stomach. In Figure 2, coil 1
By applying a high frequency current to the magnetic probe 5,
Reduce the maximum magnetization strength, preferably 10kA/■
I tried to keep it below. In this way, by lowering the sensitivity to magnetism, when the tip of the magnetic probe 5 approaches the surface of the sample 6, the magnetic force acting thereon becomes smaller, and the distance between the sample and the magnetic probe is sufficiently reduced to less than 9, for example, 1 nm. did it. In this state, a tensile or repulsive force, that is, an interatomic force, acts between the atoms on the sample surface and the atoms forming the magnetic probe. The cantilever 1 was deflected by this atomic force. The amount of deflection of the cantilever 1 was detected as a tunnel current using a probe provided behind it. By controlling the piezoelectric elements 8 in two directions forming the Tribot 9 so as to keep the value of the tunneling current constant, information on the morphology of the sample surface was obtained.

From the measurement results of the magnetic force information of Examples 2 to 5 and the surface morphology information of this example, the surface morphology information included in the measurement results of the magnetic force information can be removed, and accurate magnetic force information can be obtained. In other words, it was possible to separate and measure the magnetic information and surface morphology information of the magnetic sample.

Example 6 An example in which the magnetic probe of the present invention is applied to a magnetic recording/reproducing system will be explained with reference to FIG.

The magnetic probe 5 includes a magnetic needle 22 with a sharp tip and a magnetic path 21.
These are integrally formed on the surface of the cantilever 1. A coil 10 was provided at one end of the magnetic probe 5. The magnitude and direction of magnetization at the tip of the magnetic needle 22 are determined by the coil 1.
This was controlled by arbitrarily changing the direction and magnitude of the current flowing through the current. The coil current control system was configured in the same manner as in Examples 2-5.

For magnetic recording, i! The tip of the magnetic needle 22 is brought close to the surface of the magnetic recording film 23, and in this state, the coil 10 is energized to magnetize the tip of the magnetic needle 22 so as to generate a magnetic field larger than the coercive force of the magnetic recording film 23. death.

The magnetic recording film 23 was magnetized by the magnetization of the magnetic needle 22.

The direction of magnetization of the magnetic needle 22 was changed by changing the direction of energization to the coil 10. The magnitude of magnetization during magnetic recording was set to be larger than the coercive force of the magnetic recording film 23. On the other hand, recorded signals were reproduced from the magnetically recorded magnetic recording film 23 in the following manner. The coil 10 was energized to magnetize the tip of the magnetic needle 22, and the tip of the magnetic needle was brought close to the surface of the magnetic recording film. The magnitude of magnetization at this time is the magnetic recording film 2
The coercive force was set smaller than that of No. 3. When the magnetic recording film 23 is moved in this state as shown by the arrow 24, a magnetic force of tension or repulsion acts between the magnetic needles 22 in accordance with the direction of magnetization of the magnetic recording film 23, and as a result, the cantilever 1
is subjected to deflection. The displacement due to the bending of the cantilever 1 is
Detection was performed by an optical displacement detection system 25 provided behind the cantilever. The displacement detection system 25 may use an optical method to detect the displacement of the cantilever 1 as a change in the phase of light.

Alternatively, it goes without saying that similar effects can be obtained by detecting changes in tunnel current as in Examples 2 to 5, or even detecting changes in capacitance.

[Effects of the Invention] As described above, a magnetic probe is formed on the surface of a cantilever with a sharp tip, and the magnitude and direction of magnetization at the tip of the magnetic probe can be arbitrarily controlled. By installing the tip so that it approaches the sample surface perpendicularly, and by coating the surfaces of the magnetic tip and cantilever with a coating layer made of conductive material to configure a magnetic information detection device, the magnetic force on the surface of the magnetic sample can be detected. The effect was that information and morphological information could be separated and detected with high sensitivity and high resolution.

[Brief explanation of drawings]

FIG. 1 is a diagram of one embodiment of the magnetic probe of the present invention. FIG. 2 is an explanatory diagram showing an example of application of the magnetic probe of the present invention to a magnetic force microscope and an atomic open force microscope, and FIG. An explanatory diagram of an example of application to a magnetic force microscope using the magnetic probe of the present invention, Fig. 4 is an explanatory diagram of another example of application to a magnetic force microscope using the magnetic probe of the present invention, Fig. 5 7 is an explanatory diagram of an embodiment in which the present invention is applied to a magnetic recording and reproducing system. Explanation of symbols 1: Cantilever 2: Support, 3: Hole, 4: Tip. 5: magnetic probe, 6: sample, 7: v probe, 8: piezoelectric element. 9 dry pot, 10: coil, 11: current tester. 12: Constant current servo circuit, 13: Two-dimensional scanning system, 14
: Display, 15: Coil current control circuit, 21: Magnetic path. 22: Magnetic needle, 23: Magnetic recording film, 24: Arrow, 25:
Displacement detection system.

Claims (1)

[Claims] 1. A cantilever with a sharp tip, a magnetic probe formed at the tip of the cantilever, and detection of displacement of the cantilever due to magnetic force generated between the magnetic probe and a magnetic sample. 1. A magnetic information detection device, characterized in that the magnetic probe is provided with a coil for controlling the magnitude and direction of magnetization of the magnetic probe. 2. The magnetic force detection device according to claim 1, wherein the magnetic probe is formed of a thin film of magnetic material. 3. The magnetic information detection device according to claim 1, wherein the magnetic probe has a coercive force of 80 kA/m or less. 4. The magnetic information detecting device according to claim 1, wherein the tip of the magnetic probe is placed facing perpendicularly or parallel to the sample surface. 5. Claim 1, wherein the magnetic probe is composed of a magnetic needle, and its axis of easy magnetization is oriented perpendicularly or parallel to the sample surface. Magnetic information detection device described in Section 1.