JPH04116401A - Device and method of observing magnetic field - Google Patents

Abstract

PURPOSE: To observe a magnetic field in the vicinity of the surface of a sample in scanning tunnel michroscopic mode by providing means for extracting the specific frequency component of a tunneling current generated through interaction of the magnetic field and magnetic moment. CONSTITUTION: The magnetic field observing system comprises a cantilever 16, a chip 12 supported on a cantilever 16 and having a magnetic moment at least at the forward end thereof, and means for applying a voltage between the chip 12 and the surface of a sample. The system further comprises means for keeping a distance between the chip 12 and the surface of a sample at a level permitting a tunnel current flow, and means for extracting a specific frequency component of a tunnel current generated through interaction of a magnetic field connected electrically with the chip 12 and the magnetic moment. While keeping the distance between the chip 12 and the surface of the sample at a level permitting a tunnel current flow, a magnetic field alternating at a specific frequency is generated and the chip 12 is oscillated through interaction of the magnetic moment and the magnetic field. Finaly, the specific frequency component of the tunnel current is extracted.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to an apparatus and method for observing a magnetic field near the surface of a sample. More specifically, the scanning tunneling microscope (ST
Regarding M).

B. Prior Art In recent years, the recording density of magnetic recording devices has been improving. In order to investigate defects in the components of such devices, it is important to observe the surface shape with nanometer precision and to observe the magnetic field generated near the surface. In order to investigate the influence of the surface shape on the magnetic field, it is most desirable to observe both at the same time.

Martin et al. propose a magnetic force microscope (MFM) using the principle of an atomic open force microscope in the following document.

(1) Y, Martin, H, Wickram
asinghe, ”Magneticimagin
g by 'force m1croscopy' w
ith 1000 people resolution, App
l, Phys, LetL,, 50(20),
pp, 1455-1457. 18 May 198
7゜(2) P, C, D, Hobbs, D, W-A
braham, and il, wickram
asinghe, ”Magnetic force
m1croscopy with 25nm res
solution, Appl, Phys,
Lett, 55(22), pp, 2357-23
59. 27 November 1989 These conventional MFMs constantly vibrate a cantilever, on which a tip made of a magnetic material is mounted, in the vicinity of its resonant frequency, and use an interferometer or other device to measure the amplitude shift that occurs when the tip senses magnetic force. to observe optically. As data regarding the magnetic field, the first-order differential or second-order differential of the magnetic field can be obtained. If the same device is used, but instead of magnetic force, the tip is made to sense the interatomic force acting between the atoms at the tip of the tip and the atoms on the surface of the sample, the surface shape can be observed.

In this manner, in the devices (1) and (2) above, not only the magnetic force but also the surface shape is reduced to a force acting on the tip of the tip and observed. Therefore, it is extremely difficult to simultaneously observe magnetic force and surface topography, since the effects of the two forces must be distinguished from the observed amplitude shifts. Furthermore, setting up an optical system for optically observing the amplitude of the cantilever is complicated.

In addition to being difficult to adjust and operate, MFM is not yet commercially available. Therefore, S is available commercially and is relatively easy to adjust and operate.
A device that can observe magnetic fields using TM is desired.

Attempts have also been made to simultaneously observe the surface shape and the force acting on the chip using STM, which are disclosed in the following documents.

(3) N.A. Taubenblatt, “La.
teral forces and t.

pography using the scanni
ng tunneling m1croscope a
nd optical sensing of the
tip position.

IBM Technical Disclosure
Bulletin, Vol, 32°No, 3A, pp
, 250-251. August 1989゜(4
) U, Durig, J., Gimzewski,
and D., W., Pohl.

Experimental 0bservation
of Forces Acting during S
canning tunneling microsc
opy, Phys, Rev, Lett,, V
ol, 57. No, 19. pp, 2403-240
6. November 1986 Among these, the device (3) has the same problem as the above-mentioned MFM in that the change in amplitude of the STM chip is detected optically. Furthermore, it can only detect the force that swings the tip in a direction parallel to the sample surface, making it unsuitable for observing the magnetic field generated by a magnetic head.

In the apparatus (4), as shown in FIG. 9, a gold thin film sample 100 whose surface shape is to be measured is placed on the tip of a flexible cantilever 102. Due to thermal fluctuations, the cantilever 102 has a frequency of about 0.2 near the resonance frequency.
It vibrates with minute amplitude, but it is detected in the form of the above-mentioned frequency component of tunnel current. Tungsten S
A fan works between the tip of the TM chip 104 and the sample surface.
If there is a slope of the Der Waals force, the cantilever 1
02 resonance frequency changes. Therefore, by analyzing the tunneling current with a spectrum analyzer and detecting shifts in the resonant frequency, data regarding van der Waalska can be obtained.

Data on the surface shape of the sample is obtained in the form of a signal given to the Z-direction driving means for the tip when controlling the distance between the tip 104 and the sample surface to be constant based on the tunnel current with high frequency components cut.

However, even if the chip of this device is made of a magnetic material, it is difficult to observe both the surface shape and magnetic field of the thin-film magnetic head for the following reasons.

(I) Usually, the magnetic head is integrated with the slider. Additionally, wires are attached for supplying the current to generate the magnetic field. Therefore, the weight of the sample will be much greater than a thin film of gold.

It is difficult to prepare a flexible cantilever that can support such a heavy sample.

(II) In order to distinguish between changes in tunneling current due to force and those due to surface topography, the frequency of the sample and therefore the cantilever must be high. However, it is difficult to place a heavy sample such as a magnetic head on a cantilever and vibrate it at high frequency. Even if it were possible to vibrate at a high frequency, the amplitude would be so small that it would be difficult to detect a shift in the resonant frequency.

(Ill) Since the sample and sample stage, which are much heavier and have a larger volume than the chip, vibrate, they are more susceptible to noise and the S/N ratio of the measurement results decreases. In this case, noise refers to air vibrations such as wind and sound waves, and vibrations transmitted through the seismic stand.

In short, when trying to view a sample with a large volume and mass using AIJ with a small STM chip, it is unnatural to move the sample. Therefore, a measurement device is desired that can simultaneously acquire surface shape and magnetic field data without moving the sample.

C1 Problems to be Solved by the Invention Therefore, the purpose of the present invention is to provide a new device that can observe the magnetic field near the sample surface with simple operations in the STM mode, which measures the tunneling current while scanning the tip along the sample surface. It is about providing.

Another object of the present invention is to provide an apparatus and method that can simultaneously observe the surface shape of even a heavy sample and the magnetic field directly above the surface in the STM mode.

]9 Yet another object of the present invention is to enable observation of magnetic fields using a conventional STM with slight modifications.

01 Means for Solving the Problems According to one aspect of the present invention, there is provided an apparatus for observing a magnetic field alternating at a predetermined frequency near the surface of a sample whose surface is electrically conductive, the apparatus comprising: (a) a cantilever; (b) a tip supported by the cantilever and having at least a tip having a magnetic moment; (c) means for applying a voltage between the depth and the sample surface; (d) the tip and the sample surface. (e) electrically connected to the chip, for extracting the predetermined frequency component of the tunnel current generated as a result of the interaction between the magnetic field and the magnetic moment; An observation device comprising means is provided.

The magnetic field observation force method using such a novel STM is as follows: (a) While maintaining the distance between the tip and the sample surface at a distance that allows tunneling current to flow, a magnetic field alternating at the predetermined frequency is generated, and the magnetic field is vibrating the tip by causing a moment to interact with the magnetic field; and (b) extracting the predetermined frequency component of the l-channel current.

According to another aspect of the present invention, there is provided an apparatus for observing a magnetic field near the surface of a sample having at least a conductive surface, the apparatus comprising: (a) a cantilever; (b) a cantilever supported by the cantilever and at least a tip thereof a chip whose surface is magnetic; (c) means for switching the direction of the magnetic moment of the chip at a predetermined frequency; (d) means for applying a voltage between the chip and the sample surface; ) a means for maintaining the distance between the tip and the sample surface at a distance that allows tunneling current to flow; An observation device is provided that includes means for extracting the predetermined frequency component.

A magnetic field observation method using such a novel STM includes: (a) switching the direction of the magnetic moment of the tip at a predetermined frequency while maintaining the distance between the tip and the sample surface at a distance that allows tunneling current to flow; The method is characterized by comprising the steps of: vibrating the tip by causing the magnetic moment to interact with the magnetic field; and (b) extracting the predetermined frequency component of the tunnel current.

In any aspect of the present invention, when the chip is scanned along the sample surface, the step of (c) cutting off the high frequency components of the tunnel current; (d) the step of cutting the high frequency components of the tunnel current; By adding the step of determining the output of the Z-direction control means so that the current is constant, it becomes possible to simultaneously observe the shape of the sample surface.

E. Example 1 FIG. 1 shows the configuration of an apparatus that uses an STM unit 10 having a chip 12 to simultaneously observe the surface shape of a sample 14, which is a thin film magnetic head, and the alternating current magnetic field generated in the vicinity thereof. If a tip attached to a cantilever and having at least a magnetic moment at the tip is prepared, the STM unit 10 can be used as a currently commercially available one by simply replacing the tip.

As is well known, STM is used to observe the shape of a conductive sample surface. Therefore, in order to observe the surface of a non-conductive sample using STM, it is necessary to attach a conductive substance thereon. To inspect a thin-film magnetic head, it is sufficient to have a resolution of several hundred people, so 10
A film of PT or the like having a thickness of about 0 to 200 mm may be deposited uniformly by sputtering.

FIG. 2 is an enlarged view of the chip 12 and its surroundings. The tip 12 is attached to the free end of a cantilever 16 that extends in a direction parallel to the sample surface. In this example, the tip 12 has a radius of curvature of approximately 0.1 μm and a length Ll of 2
00-300u, m. Further, the cantilever 16 of this example has a length L2 of about 700 um and a diameter of about 1100 um.
It is u.

One end of the cantilever 16 is fixed to the piezo element 20.22.24 by a member 18 extending in the Z direction. The member 18 has a diameter of 250 μm in this example. Of course, members 16 and 18 can be integrally molded. The piezo elements 20, 22, 24 are connected to the cantilever 1, respectively.
6. Therefore, the tip 12 is moved in the x, y, z directions and scanned along the sample surface while keeping the tip at a distance from the sample surface that allows the tunneling current to flow. be. Here, the X% y direction is parallel to the sample surface, and the Z
The direction is perpendicular to the same surface. The axial direction of the chip is Z
consistent with the direction.

At least the tip surface of the tip 12 is made of Fe.

It must be made of a magnetic material such as Ni. The entire chip 12, including its interior, may be made of ferromagnetic material. chip 1
2 and the cantilever 16 may be molded integrally, or may be molded separately and joined later.

Generally, when a magnet takes the shape of a sharp needle, such as the tip of an STM tip, due to shape anisotropy, the magnetic moment points in the axial direction of the needle, and that direction is in accordance with the direction of the external magnetic field. Almost unaffected.

Therefore, an attractive force or a repulsive force in the Z direction acts on the tip of the tip 12 due to the magnetic field generated near the sample surface. Furthermore, since the tip of the tip 12 can be brought close to the sample surface by several tens of angstroms, it is also affected by non-magnetic forces such as van der Waals forces. Therefore, the force F2 in the Z direction acting on the tip of the tip 12 is expressed by the following formula (1)
It is expressed as

However, Fn is a non-magnetic force such as van der Waals force, and ■ is the magnetic moment zt of the tip tip.
j is the magnitude of the magnetic field H generated near the sample surface, r is the position vector, and t is the time.

The sum of these forces is applied to the cantilever 16, and as a result of the cantilever being bent, the tip of the tip 12 is displaced in the Z direction. The displacement amount δ2 is determined as shown in the following equation (2).

Here, I is the moment of inertia, L is the length of the arm of the cantilever, E is Young's modulus, and d is the spring constant of the cantilever.

In the present invention, in addition to changing the distance between the tip and the sample surface due to the unevenness of the sample surface, the distance between the tip and the sample surface also changes by δ2 due to the deflection of the cantilever, so the tunneling current JT is calculated using the following equation ( 3) changes as given by.

Here, Z is the distance between the sample surface and the tip when the cantilever is not bent, Φ is the work function (work required to emit electrons from the sample surface), and Jo and A are constants.

In FIG. 1, the x and y direction control circuit 30 is a chip]
A voltage signal for scanning 2 in the x and y directions is supplied to a piezo element for driving in the x and y directions.

The Z-direction control circuit 32 supplies a voltage signal for moving the chip 12 in the Z-direction to a piezo element for driving in the Z-direction.

Specifically, these circuits may be transistor circuits that generate a high voltage of about 1.00V.

In normal STM, while keeping the tunnel current constant,
The chip is scanned in the x and y directions. When the tip comes to a convex part of the sample surface, the tunnel current increases, so the tip is raised to the position where the original current is restored, and conversely, the tip is lowered at an open part. By repeating this operation and capturing the changes in the voltage applied to the piezo element and creating an image, it is possible to observe the surface structure on an atomic scale.

In the present invention, surface shape observation is basically performed based on the same principle. However, in the device of the present invention, the distance between the tip and the sample surface is not determined only by the shape of the sample surface, but is also affected by the force acting on the tip tip. Therefore, both influences coexist on the tunnel current. In order to accurately determine the sample surface shape or force, it is necessary to separate the effects of these two factors. To this end, the present invention utilizes the fact that the magnetic field generated by the magnetic head is an alternating magnetic field.

As shown in FIGS. 1 and 3, the coil of the magnetic head 14 is supplied with an alternating current signal generated by an oscillator 40, thereby generating an alternating magnetic field.

The output of oscillator 40 is also used as a reference signal (Rer) for lock-in amplifier 42. Now, the AC signal given to the magnetic head has an angular frequency ω. Suppose that it is a sine wave. At this time, the Z component Hz of the alternating current magnetic field H generated by the magnetic head is expressed by the following equation (4).

H=(r, t) −H−(r) cosωot (
4,) Under such an alternating magnetic field, the deflection δ2 of the free end of the cantilever is expressed by the following equation (5).

Here, H, (r) is abbreviated as I(,. As can be seen from the above equation, the tip vibrates at an angular frequency ω.

Therefore, the tunneling current is modulated. From this modulated tunnel current, the angular frequency ω is generated through the lock-in amplifier 42. Extract the components of

The output f (J) of the lock-in amplifier 42 is expressed by the following equation 4.
Formula % Therefore, the logarithm of f(J) is the magnetic force maH,,/aZ
, that is, it is proportional to the magnetic field gradient θ1/aZ.

The magnitude of the magnetic field gradient a I-I,/az is the angular frequency ω of the tunneling current extracted through the lock-in amplifier 42. It is calculated from the amplitude of the component. On the other hand, the sign of the magnetic field gradient a H, / a z is the angular frequency ω of the tunneling current. It is determined from the phase of the components of. For example, magnetic pole 1 in Fig.
c in the vicinity of ? If the sign of H,/a z is positive, the gradient of the magnetic field near magnetic pole 2 is 9H.

The sign of /aZ is negative. This is because the phase of the component of the angular frequency ω0 of the tunnel current is shifted by 1800 in the vicinity of the magnetic pole 1 and the magnetic pole 2. Such a phase shift is detected in the lock-in amplifier 42 by comparing the tunnel current with a reference signal (Rer).

As shown in FIG. 1, the tunneling current is also supplied to a low pass filter (LPF) 44 connected in parallel to the lock-in amplifier 42. LPF44
The output of is supplied to a feedback circuit 46. Fourth
As shown in the figure, the cutoff frequency ω of the LPF 44. is the frequency of the alternating magnetic field, that is, the peak ω of the alternating current component of the tunnel current.
. By setting it sufficiently lower, the influence of the magnetic field can be removed from the tunnel current. In FIG. 4, curve A shows the characteristics of the LPF, and curve B shows the spectrum of the alternating current component of the tunnel current. Generally, the frequency of the alternating current magnetic field generated by a thin film magnetic head is 10 to 20kHz.
z, it is easy to set such a cutoff frequency. The output of the LPF 44 is affected only by the sample surface shape. Feedback circuit 46 is an LPF
44 is compared with a reference value, and a feedback signal is supplied to the Z direction control circuit 32 in order to eliminate the difference between the two. The Z-direction control circuit 32 supplies a voltage signal according to the feedback signal to a piezo element for driving in the Z-direction.

As a result, the distance between the tip and the sample surface, excluding the influence of tip vibration, is kept constant.

In this example, the alternating current signal applied to the magnetic head was a sine wave, but even when a rectangular wave with a constant frequency is applied, the influence of the sample surface shape and the influence of the magnetic field can be separated using the same method.

The surface shape is visualized by the surface shape visualization device 50 according to the outputs of the x, X direction control circuit 30 and the Z direction control circuit 32. The data regarding the magnetic field, in this case the distribution of El
2, Xl, and the output of the X-direction control circuit 3o, the magnetic field gradient distribution is visualized by the magnetic field gradient distribution visualization device 52. The surface shape visualization device 50 and the magnetic field gradient distribution visualization device 52 are, for example, computers equipped with a display. Note that the x, X direction control circuit 30. Z direction control circuit 3
The level of the signal supplied from the circuit 2 to the STM unit 10 and the level of the signal supplied from the circuit 30.32 to the visualization device 50.52 need only be in a proportional relationship, and the levels must match. There's no need to be.

FIG. 5 is an example of the image output of the surface shape of the side portion of the thin film magnetic head. The y-axis and the y-axis correspond to the X-scanning direction and the X-scanning direction of the chip, respectively.

The y-axis represents the height of the sample surface. The chip is scanned approximately 8μ in the X direction and approximately 2μ in the X direction. Here, the numbers on each axis' scale provide a relative measure. FIG. 6 is an image output of the simultaneously measured magnetic field gradient distribution corresponding to FIG. The numbers on the y-axis scale indicate the relative magnitude of the magnetic field gradient.

FIG. 7 is an example of an image output of the surface shape of the central portion of a thin film magnetic head. The size of the scanning range is the same as in FIG. The LP part is the left magnetic pole, the G part is the gap, and the RP part is the right magnetic pole. Foreign matter is observed attached to the left magnetic pole. FIG. 8 is an example of an image output of the simultaneously measured magnetic field gradient distribution corresponding to FIG. 7. It can be seen that the value of the magnetic field gradient is lower in the area where the foreign matter is attached.

Example 2 Example 1 made it possible to observe a dynamic magnetic field such as the magnetic field generated by a magnetic head. In addition, the present invention is also applicable to observation of static magnetic fields such as those exhibited by magnetic media.

An example that enables such observation will be described below.

The tip of the tip of a dynamic magnetic field measurement device is a magnet with a magnetic moment fixed in one direction, whereas the tip of a static magnetic field measurement device is configured so that the direction of the magnetic moment switches at a predetermined frequency. . Specifically, an alternating current magnetic field is generated by winding a coil around the chip, connecting an oscillator to the coil, and applying an alternating current signal of a predetermined frequency. This alternating magnetic field generates a magnetic moment at least at the tip of the tip, and its direction is switched at the predetermined frequency. The alternating current signal may be a sine wave or a square wave.

Therefore, in order to measure a static magnetic field, it is required that the direction of the magnetic moment of the chip be alternated.

An example of a chip structure that can meet such requirements is Sueoka et al., “Magnetic field imaging by Fe-coated M, FM chips,” Proceedings of the 3rd Applied Physics Association Conference, 31a PA- 9゜part II, P, 43
4. Disclosed in March 1000. According to it,
The chip body is made of tungsten, and the surface has a thickness of 10
A thin Fe film of 0.00 to 2000% can be deposited by sputtering.

As in Example 1, the interaction between the magnetic moment and the magnetic field causes a magnetic force to act on the tip, causing the cantilever to bend. Therefore, by extracting the predetermined frequency component from the tunnel current using a lock-in amplifier, the magnitude of the gradient of the magnetic field near the surface can be determined. Further, the sign of the gradient of the magnetic field is determined from the phase of the predetermined frequency component of the tunnel current. For example, in the case of a perpendicularly magnetized film, if the sign of the magnetic field gradient is positive just above the magnetic domain where the medium surface is the north pole, the sign of the magnetic field gradient is negative just above the magnetic domain where the medium surface is the south pole. Become. This is because the phase of the predetermined frequency component of the tunnel current detected by the lock-in amplifier is shifted by 1800 on the former and latter magnetic domains.

Note that the magnetic field on the medium surface observed in this way was at a distance of several tens of angstroms from the sample surface, so it can be said that the pattern of magnetic domains formed in the medium could be observed. However, in order to successfully observe the magnetic domain pattern on the medium, it is required that the strength of the magnetic field created by the magnetic moment at the tip of the tip on the surface of the medium be smaller than the coercive force Hc of the medium. In order to meet this requirement, it is necessary to appropriately determine the number of turns of the coil and the value of the current flowing through the coil.

As in Example 1, if the output of the Z-direction control circuit is determined so that the tunnel current with high frequency components cut is constant, the shape of the sample surface can be determined using the outputs of the X-, V-, and Z-direction control circuits. It is also possible to visualize it.

Modifications The present invention can also be applied to the case of observing the magnetic field at one point without moving the chip.

Furthermore, although the gradient of the magnetic field is primarily visualized in the above example, it is also possible to process the data to visualize other data such as the Z component of the magnetic field or its second order differential. Of course, such data can also be stored in a storage device without being visualized immediately.

F1 Effects of the Invention According to the present invention, the magnetic field near the sample surface can be observed with a simple operation in the STM mode in which the tunnel current is measured while scanning the tip along the sample surface.

Further, according to the present invention, even if the sample is heavy, its surface shape and the magnetic field directly above the surface can be observed simultaneously in the STM mode.

Furthermore, according to the present invention, magnetic fields can be observed using a conventional STM with slight modifications.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the hardware configuration of one embodiment of the present invention. FIG. 2 is an enlarged view of the chip. FIG. 3 is an explanatory diagram of the principle of magnetic field observation according to the embodiment described in -. FIG. 4 is a diagram showing the frequency characteristics of the LPF used in the present invention. FIG. 5 is a graph showing an example of the observation results of the sample surface shape. FIG. 6 is a graph showing the observation results of the magnetic field corresponding to FIG. FIG. 7 is a graph showing another example of the observation results of the sample surface shape. FIG. 8 is a graph showing the observation results of the magnetic field corresponding to FIG. FIG. 9 is an explanatory diagram of a conventional device for simultaneously measuring sample surface shape and force using STM. Applicant International Business Machines Corporation Representative Patent Attorney Takashi Tongu (alias) Z-axis

Claims (28)

[Claims] (1) At least near the surface of the sample whose surface is conductive,
An apparatus for observing a magnetic field alternating at a predetermined frequency, comprising: (a) a cantilever; (b) a tip supported by the cantilever and having at least a magnetic moment at its tip; and (c) the tip and the sample surface. (d) means for maintaining the distance between the tip and the sample surface at a distance that allows a tunnel current to flow; (e) the magnetic field electrically connected to the tip; An observation device comprising means for extracting the predetermined frequency component of the tunnel current generated as a result of the interaction of the magnetic moments. 2. The apparatus according to claim 1, further comprising means for visualizing data regarding the magnetic field using the output of the means (e). (3) When the direction perpendicular to the sample surface is defined as the z direction,
3. A device according to claim 1 or 2, wherein at least the tip of the tip has a magnetic moment in the z-direction, and the tip is subjected to a force when there is a gradient in the z-direction of the z-component of the magnetic field. (4) An apparatus for simultaneously observing the surface shape of a sample having at least a conductive surface and a magnetic field alternating at a predetermined frequency in the vicinity of the sample surface, the apparatus comprising: (a) a cantilever; (c) means for applying a voltage between the tip and the sample surface; (d) a direction parallel to the sample surface in the x and y directions; When the direction perpendicular to the sample surface is the z direction, an x direction driving means, a y direction driving means, and a z direction driving means for moving the chip in the x, y, and z directions according to each input signal; (e) In order to scan the chip in the x and y directions while keeping the distance between the chip and the sample surface at a distance that allows tunneling current to flow in two directions, the x-direction driving means, the y-direction driving means, and x-direction control means, y-direction control means, and z-direction control means for providing signals to the z-direction drive means; (f) electrically connected to said chip, generated as a result of the interaction of said magnetic field and said magnetic moment; (g) a low-pass filter electrically connected to the chip; (h) means for controlling the z-direction so that the output of the low-pass filter is constant; an observation device comprising means for determining the output of (5) The apparatus according to claim 4, further comprising means for visualizing the sample surface shape using the outputs of the x-direction control means, the y-direction control means, and the z-direction control means. (6) The apparatus according to claim 4 or 5, further comprising means for visualizing data regarding the magnetic field using the outputs of the x-direction control means, the y-direction control means, and the means (f). (7) The device according to any one of claims 4 to 6, wherein at least the tip of the tip has a magnetic moment in the z direction, and the tip receives a force when there is a gradient in the z direction of the z component of the magnetic field. . (8) An apparatus for observing a magnetic field near the surface of a sample having at least a conductive surface, the device comprising: (a) a cantilever; and (b) a chip supported by the cantilever and having at least the surface of its tip made of a magnetic material. (c) means for switching the direction of the magnetic moment of the tip at a predetermined frequency; (d) means for applying a voltage between the tip and the sample surface; (e) the tip and the sample surface. (f) electrically connected to the chip, for extracting the predetermined frequency component of the tunnel current generated as a result of the interaction between the magnetic field and the magnetic moment; An observation device equipped with means. (9) The apparatus according to claim 8, further comprising means for visualizing data regarding the magnetic field using the output of the means (f). (10) When the direction perpendicular to the sample surface is defined as the z direction, a magnetic moment in the z direction is generated in the tip, and the tip receives a force when there is a gradient in the z direction of the z component of the magnetic field. The device according to claim 8 or 9. (11) An apparatus for simultaneously observing the surface shape of a sample whose surface is electrically conductive and the magnetic field near the sample surface, comprising: (a) a cantilever; (b) a device supported by the cantilever and having at least a tip a chip whose surface is magnetic; (c) means for switching the direction of the magnetic moment of the chip at a predetermined frequency; (d) means for applying a voltage between the chip and the sample surface; ) When the x and y directions are parallel to the sample surface and the z direction is perpendicular to the sample surface, the x direction is for moving the chip in the x, y, and z directions according to each input signal. a driving means, a y-direction driving means, and a z-direction driving means; (f) scanning the chip in the x and y directions while keeping the distance between the chip and the sample surface in the z-direction at a distance that allows a tunnel current to flow; (g) electrically connected to the chip; and (g) electrically connected to the chip. means for extracting the predetermined frequency component of the tunnel current generated as a result of the interaction between the magnetic field and the magnetic moment; (h) a low-pass filter electrically connected to the chip; An observation device comprising means for determining the output of the z-direction control means so that the output of the low-pass filter is constant. (12) The apparatus according to claim 12, further comprising means for visualizing the sample surface shape according to the outputs of the x-direction control means, the y-direction control means, and the z-direction control means. (13) The apparatus according to claim 11 or 12, further comprising means for visualizing data regarding the magnetic field according to the outputs of the x-direction control means, the y-direction control means, and the means (g). (14) The device according to any one of claims 11 to 13, wherein a magnetic moment in the z-direction is generated in the tip, and the tip is subjected to a force when there is a gradient in the z-direction of the z-component of the magnetic field. (15) To observe a magnetic field alternating at a predetermined frequency near the surface of a sample whose surface is at least electrically conductive using an STM equipped with a cantilever and a tip supported by the cantilever and having at least a magnetic moment at its tip. (a) generating a magnetic field alternating at the predetermined frequency while maintaining the distance between the tip and the sample surface at a distance that allows tunneling current to flow, and causing the magnetic moment to interact with the magnetic field; An observation method comprising: vibrating the chip; and (b) extracting the predetermined frequency component of the tunnel current. (16) The method according to claim 15, further comprising the step of visualizing data regarding the magnetic field using the predetermined frequency component of the tunneling current extracted in step (b). (17) When the direction perpendicular to the sample surface is the z direction, at least the tip of the tip has a magnetic moment in the z direction, and in step (a) the tip has a magnetic moment in the z direction of the z component of the magnetic field. 17. The method according to claim 15 or 16, wherein the force is applied when the is present. (18) a cantilever; a chip supported by the cantilever and having at least a tip having a magnetic moment;
When the directions parallel to the sample surface are x and y directions, and the directions perpendicular to the sample surface are z directions, x to move the chip in x, y, and z directions according to each input signal
directional driving means, y-direction driving means, and z-direction driving means; A method for simultaneously observing the surface shape of a sample having at least a conductive surface and a magnetic field alternating at a predetermined frequency in the vicinity of the sample surface using an STM equipped with a control means, the method comprising: (a) the above-mentioned chip; While scanning the tip along the sample surface while keeping the distance between the tip and the sample surface at a distance that allows tunneling current to flow, a magnetic field alternating at the predetermined frequency is generated, and the magnetic moment interacts with the magnetic field. (b) extracting the predetermined frequency component of the tunnel current; (c) cutting the high frequency component of the tunnel current including the predetermined frequency; (d) An observation method including the step of determining the output of the z-direction control means so that the tunnel current after cutting high frequency components is constant. (19) The method according to claim 18, further comprising the step of visualizing the sample surface shape using the outputs of the x-direction control means, the y-direction control means, and the z-direction control means. (20) Claim 18, further comprising the step of visualizing data regarding the magnetic field using the outputs of the x-direction control means and the y-direction control means and the predetermined frequency component of the tunnel current extracted in step (b). 19. The method described in 19. (21) At least the tip of the tip has a magnetic moment in the z direction, and in step (a) the tip is subjected to a force when there is a gradient in the z direction of the z component of the magnetic field. Any method described. (22) A method for observing a magnetic field near the surface of a sample whose surface is electrically conductive, using an STM equipped with a cantilever and a tip supported by the cantilever and whose tip surface is a magnetic material. (a) Switching the direction of the magnetic moment of the tip at a predetermined frequency while maintaining the distance between the tip and the surface of the sample at a distance that allows tunneling current to flow, and causing the magnetic moment to interact with the magnetic field. An observation method comprising: vibrating the chip; and (b) extracting the predetermined frequency component of the tunnel current. (23) The method according to claim 22, further comprising the step of visualizing data regarding the magnetic field using the predetermined frequency component of the tunneling current extracted in step (b). (24) When the direction perpendicular to the sample surface is defined as the z direction, in the step (a), a magnetic moment in the z direction is generated in the tip, and the tip has a gradient in the z direction of the z component of the magnetic field. Claim 22: The force is applied when the
or the method described in 23. (25) When a cantilever and a chip supported by the cantilever and having at least the surface of the tip are magnetic, the x and y directions are parallel to the sample surface, and the z direction is perpendicular to the sample surface. , x-direction driving means, y-direction driving means, and z-direction driving means for moving the chip in the x, y, and z directions according to respective input signals, and the x-direction driving means, y-direction driving means, respectively; and x-direction control means, y-direction control means, and z-direction control means for providing a signal to the z-direction drive means,
A method for simultaneously observing the surface shape of a sample having at least a conductive surface and the magnetic field near the sample surface, the method comprising: (a) keeping the distance between the tip and the sample surface at a distance that allows a tunneling current to flow; , while scanning the tip along the sample surface, switching the direction of the magnetic moment of the tip at a predetermined frequency, and causing the magnetic moment to interact with the magnetic field to vibrate the tip; (b) extracting the predetermined frequency component of the tunnel current; (c) cutting the high frequency component of the tunnel current including the predetermined frequency; and (d) ensuring that the tunnel current after cutting the high frequency component remains constant. An observation method comprising the step of determining an output of the z-direction control means. (26) The method according to claim 25, further comprising the step of visualizing the sample surface shape using the outputs of the x-direction control means, the y-direction control means, and the z-direction control means. (27) Claim 25, further comprising the step of visualizing data regarding the magnetic field using the outputs of the x-direction control means and the y-direction control means and the predetermined frequency component of the tunnel current extracted in step (b). 26. The method described in 26. (28) In the step (a), a magnetic moment in the z-direction is generated in the chip, and the chip receives a force when there is a gradient in the z-direction of the z-component of the magnetic field. Method described in Crab.