JPH1123591A - Scanning type magnetic microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a scanning type magnetic microscope capable of measuring the micro-magnetic distribution on the surface of a magnetic material and the surface construction by high spatial resolution and high sensitivity. SOLUTION: This scanning type magnetic microscope is provided with a flexible cantilever 1 having a probe 1a on the extreme end, a superconducting quantum interference element (SQUID) 2 for detecting the intensity of the magnetic field on the extreme end position of the cantilever 1, and the cooling device 10, and by scanning the probe 1a along the surface of a sample S while holding the distance between the probe 1a of the cantilever 1 and the surface of the sample S, the construction information of the surface of the sample is detected through observation using interatomic force and tunnel current, and the magnetic information on the sample of the same place is measured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning magnetic microscope suitable for measuring minute magnetic distribution and surface structure of a magnetic sample surface with high spatial resolution and high sensitivity.

[0002]

2. Description of the Related Art As a magnetic force microscope, a probe made of a magnetic material is used, and a magnetization state of a sample is examined by using a magnetic force generated between the magnetic probe and a magnetic field leaking to the surface of a magnetic sample. Structured devices are known.

Conventionally, a method of acquiring magnetic information of a sample used in a scanning magnetic force microscope using a magnetic force obtained by approaching a magnetic probe of this type and a sample has been described.
Literature; Applied Physics Letters, Vol. 50 (1987), pp. 1455-1457. A typical method for detecting magnetic information is to scan the sample surface with a magnetic probe at the tip of the cantilever in a region where the magnetic force acts on the sample surface (several tens of nm or less from the surface), and detect a change in the force acting on the cantilever. And the distribution of magnetic force.

[0004]

By the way, in the conventional magnetic force microscope employing the above-described magnetic information detection method, the magnetic probe acting on the magnetic probe is maintained so that the magnetic force or the magnetic force gradient acting on the magnetic probe is kept constant. By controlling the position, the distribution of the stray magnetic field on the sample surface can be measured. However, since the magnetic distribution and the information of the surface shape are measured together, it is difficult to measure true magnetic information.

That is, since the magnetic force acting between the magnetic probe and the sample is small, the magnetic probe must be brought close to the sample, and it is difficult to separate from the surface structure of the sample by the action of the atomic force. there were.

The present invention has been made in view of such circumstances, and it is possible to accurately detect the morphological information of a sample surface by observation using an atomic force or a tunnel current, and furthermore, it is possible to detect the morphological information on a sample at the same place. It is an object of the present invention to provide a scanning magnetic microscope capable of accurately measuring magnetic information.

[0007]

In order to achieve the above object, a scanning magnetic microscope according to the present invention comprises a flexible cantilever 1 having a probe 1a at a tip end as shown in FIG.
And a superconducting quantum interference device 2 (hereinafter, SQUI) for detecting the strength of the magnetic field at the tip position of the cantilever 1.
ID2) and means for scanning the probe 1a along the surface of the sample S while maintaining a constant distance between the probe 1a of the cantilever 1 and the surface of the sample S (for example, the position detector 5,
(Non-magnetic stage 7, Z-axis piezoelectric element 8, servo controller 6, etc.), and means 10 for cooling SQUID 2 to a superconducting transition temperature or lower.

In the above configuration, when the probe 1a provided at the tip of the flexible cantilever 1 is brought close to the surface of the sample S, an attractive force is first generated, and when the probe 1a is further approached, a repulsive force is generated. By the action of this atomic force, cantilever 1
Bends.

The displacement due to the bending of the cantilever 1 is
Displacement detecting means using laser light (position detector 5
And the like, so that the force acting on the probe 1a is constant based on the measurement information, that is, the deflection of the cantilever 1 is constant.
By controlling the position of the Z axis (the axis perpendicular to the sample surface), the surface structure of the sample S can be measured, and the probe 1a can be held at a constant height from the surface of the sample S. Becomes possible.

Further, the probe 1a of the cantilever 1 and the sample S
By controlling the position of the sample S or the Z axis of the sample S so that the tunnel current between the surfaces becomes constant, the sample S
Can be measured, and also in this case, the probe 1a can be held at a constant height from the surface of the sample S.

As described above, while controlling the position of the sample S or the Z-axis of the probe 1a so as to keep the displacement of the cantilever 1 constant, the strength of the magnetic field at the tip position of the cantilever 1a is measured by SQUID2. Thus, in addition to the surface information of the sample S, it is possible to simultaneously measure the magnetic information at a position at a certain distance from the surface of the sample S.

[0012]

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention. The scanning magnetic microscope according to the present embodiment includes a flexible cantilever 1 having a tip 1a having a small radius of curvature at the tip, and a position detecting device 13 for detecting displacement of the tip of the cantilever 1. The position detection device 13 is an optical lever type detection device including a laser light source 3 that irradiates the tip of the cantilever 1 with laser light, a position sensor 4 that detects reflected light thereof, and a position detector 5.

Further, the cantilever 1 is provided with a SQUID 2 disposed at the tip and a cooling device 10 for cooling the SQUID 2 to a temperature below the superconducting transition temperature.
The magnetic information measured by the SQUID control circuit 1
1 is input.

On the other hand, a non-magnetic stage 7 is disposed below the cantilever 1. This non-magnetic stage 7 is X
The sample S, which is moved in the XY directions by the Y drive circuit 12 and placed on the stage, scans the probe 1 a of the cantilever 1. Further, the non-magnetic stage 7 is provided with a Z-axis piezoelectric element 8 that applies a displacement to the sample S in the Z-axis direction (an axis perpendicular to the surface of the sample S).

In the above configuration, the output of the position detector 5 of the position detecting device 13 (displacement detection signal of the cantilever 1) is input to the servo control device 6, and the servo control device 6 responds to the displacement detection signal. The drive control of the Z-axis piezoelectric element 8 and the control signal of the Z-axis are input to the analysis / display device 9.

The analysis / display device 9 has a SQUID
The magnetic field information from the control circuit 11 is input, and the surface structure and the magnetic structure at each point of the sample S are obtained based on the information and the position information (XY axis) from the XY drive circuit 12, and the respective structures are obtained. It is configured to display information.

Next, the operation of this embodiment will be described together with the operation. When the flexible cantilever 1 having the probe 1a is brought close to the surface of the sample S, the probe 1 of the cantilever 1 is moved.
The cantilever 1 bends due to the interatomic force acting between a and the sample S. The displacement of the cantilever 1 caused by the bending is detected by the displacement detecting device 13, and the output of the device (output of the position detector 5) is input to the servo control device 6 and fed back to the Z-axis piezoelectric element 8 of the nonmagnetic stage 7. Thus, the displacement of the cantilever 1 is controlled to be constant, that is, the distance between the cantilever 1 and the sample S is kept constant.

At this time, the output of the servo controller 6 is analyzed and
By incorporating the sample S into the display device 9, the surface structure of the sample S can be measured. While the distance between the cantilever 1 and the sample S is kept constant as described above, the SQUID 2 at the tip of the cantilever 1 is cooled to a temperature lower than the superconducting transition temperature by the cooling device 10 and the output of the SQUID 2 is controlled by the SQUID control circuit. By taking it into the analysis / display device 9 via the interface 11, the intensity of the magnetic field on the surface of the sample S can be measured and displayed.

The XY drive circuit 12 scans the non-magnetic stage 7 in the X and Y directions while sequentially taking in the output signals of the servo controller 6 and the SQUID control circuit 11, thereby obtaining a sample. The surface structure at each point of S and the magnetic structure can be measured simultaneously.

Here, in the above-described embodiment, an example in which an optical lever type device is applied as the cantilever displacement detecting device has been described. However, the present invention is not limited to this. The present invention can be implemented using a displacement detection device of another method such as a tunnel current detection method.

In the above embodiment, the sample S side is displaced (XY axis and Z axis) by the movement of the non-magnetic stage 7. However, the present invention is not limited to this, and the cantilever 1 side is displaced. Then, a method of scanning the probe 1a on the surface of the sample S and controlling the position of the Z axis may be adopted.

In the present invention, as a method of detecting the strength of the magnetic field at the position of the tip of the cantilever, as shown in FIG. May be provided with only a small pickup coil, and a SQUID for its magnetic detection provided at the base of the cantilever or the like. In this case, the shape of the pickup coil may be a magnetometer or a gradiometer of various shapes.

Further, as a method of cooling the SQUID 2 (SQUID + pickup coil), in addition to the method of cooling through the heat transfer body (cantilever 1) as shown in FIG. Alternatively, a method of arranging in a refrigerant may be adopted.

[0024]

As described above, according to the present invention,
A flexible cantilever having a tip at the tip, a SQUID for detecting the strength of the magnetic field at the tip of the cantilever and its cooling means are provided, and the distance between the tip of the cantilever and the sample surface is kept constant. Since the probe is scanned along the surface of the sample while holding it, the structure of the surface of the sample can be accurately measured by observation using atomic force and tunnel current. Is detected using the SQUID, so that magnetic information can be accurately measured in addition to the surface structure of the sample.

Therefore, it is possible to realize a scanning magnetic microscope suitable for measuring a minute magnetic distribution and a surface structure on the surface of a magnetic sample with high spatial resolution and high sensitivity.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 cantilever 1 a probe 2 superconducting quantum interference device (SQUID) 3 laser light source 4 position sensor 5 position detector 6 servo controller 7 nonmagnetic stage 8 Z-axis piezoelectric element 9 analysis / display device 10 cooling device 11 SQUID control circuit 12 XY drive circuit 13 Displacement detector S sample

Claims (1)

[Claims] 1. A flexible cantilever having a probe at a tip thereof, a superconducting quantum interference device for detecting the intensity of a magnetic field at the tip of the cantilever, and a probe between the cantilever and the sample surface. While keeping the distance constant,
A scanning magnetic microscope comprising: means for scanning a probe along the surface of a sample; and means for cooling the superconducting quantum interference device to a superconducting transition temperature or lower.