JP2024087627A - Sample stage for alternating magnetic force microscope - Google Patents

Abstract

[Problem] The present invention aims to provide a sample stage for an alternating magnetic force microscope that, when used with an alternating magnetic force microscope, can generate a magnetic field with high magnetic field strength and excellent perpendicularity in the vicinity of the probe. [Solution] A sample stage for an alternating magnetic force microscope according to one aspect of the present invention comprises a housing having a cylindrical portion, a first flange portion disposed at one end of the cylindrical portion, and a second flange portion disposed on the opposite side to the one end, and a coil formed by winding a conducting wire around the cylindrical portion, and the outer surface of the first flange portion is flat. [Selected Figure] Figure 1

Description

The present invention relates to a sample stage for an alternating magnetic force microscope.

Alternating Magnetic Force Microscopy (A-MFM), a scanning probe microscopy method, generates an alternating magnetic field from below the sample to a magnetic probe placed above the sample, making it possible to detect the polarity and zero of the surface magnetic field, which was difficult to measure with conventional magnetic force microscopes (see non-patent document 1).

In an alternating magnetic force microscope, it is desirable to increase the strength of the alternating magnetic field generated by the alternating electromagnet in order to increase the measurement sensitivity. Patent Document 1 discloses an alternating electromagnet having a specific shape in order to generate a strong alternating magnetic field with low voltage and low heat generation.

JP 2017-108023 A

Jun Saito, "Alternating Magnetic Force Microscope: Achieving 5 nm Spatial Resolution and High Functionality," New Technology Briefing for the Advanced Measurement and Analysis Technology and Equipment Development Program, March 15, 2016, URL https://shingi.jst.go.jp/list/list_2015/2015_sentan.html#20160315X-002

However, in the technology described in Non-Patent Document 1, there is a large gap between the AC electromagnet that serves as the source of the alternating magnetic field and the probe to which the alternating magnetic field is applied. Therefore, even if an AC electromagnet such as that described in Non-Patent Document 1 is applied to Non-Patent Document 1 to generate a strong alternating magnetic field, the strength of the alternating magnetic field will be attenuated due to the large gap. In addition, since the magnetic field spreads as the distance from the electromagnet increases, the magnetic field perpendicularity near the probe is low, and there is a possibility that sufficient spatial resolution cannot be obtained.

The present invention has been made in consideration of the above circumstances, and aims to provide a sample stage for an alternating magnetic force microscope that, when used with an alternating magnetic force microscope, can generate a magnetic field with high magnetic field strength and excellent perpendicularity in the vicinity of the probe.

The inventors came up with the idea of shortening the distance between the alternating magnetic field source and the probe in an alternating magnetic force microscope, thereby increasing the magnetic field near the probe and making the magnetic field uniformly perpendicular, and came up with the idea of using the alternating magnetic field source as the sample stage.

The present invention has been made based on these findings, and the gist of the present invention is as follows.
[1] A sample stage for an alternating magnetic force microscope according to one aspect of the present invention includes a housing having a cylindrical portion, a first flange portion disposed at one end of the cylindrical portion, and a second flange portion disposed on the opposite side to the one end;
a coil formed by winding a conductive wire around the cylindrical portion,
The outer surface of the first flange portion is flat.
[2] The alternating magnetic force microscope sample stage described in [1] above may further include a magnetic core housed inside the cylindrical portion.
[3] The sample stage for an alternating magnetic force microscope described in [1] or [2] above may further include a ring-shaped cover made of a magnetic material and arranged on the outer periphery of the first flange portion and the conductive wire.
[4] In the sample stage for an alternating magnetic force microscope according to any one of [1] to [3] above, the housing may be made of a metal that contains mainly aluminum.
[5] In the sample stage for an alternating magnetic force microscope according to any one of [1] to [3] above, the housing may be made of polyacetal resin.
[6] In the sample stage for an alternating magnetic force microscope described in any one of [1] to [5] above, the second flange portion may be provided with a fixing portion for fixing the sample stage for an alternating magnetic force microscope.
[7] The sample stage for an alternating magnetic force microscope according to any one of [1] to [6] above may have a diameter of 25 mm or more and 37 mm or less.

When the alternating magnetic force microscope sample stage according to the above aspect is used in an alternating magnetic force microscope, it is possible to generate a magnetic field with high magnetic field strength and excellent perpendicularity in the vicinity of the probe.

1 is a perspective view of a sample stage for an alternating magnetic force microscope according to a first embodiment of the present invention; FIG. 2 is a perspective view of a housing in the embodiment. 3 is a cross-sectional view taken along line III-III in FIG. FIG. 11 is a perspective view of a sample stage for an alternating magnetic force microscope according to a second embodiment of the present invention. 4 is a cross-sectional view taken along line IV-IV in FIG. FIG. 11 is a cross-sectional view of a sample stage for an alternating magnetic force microscope according to a third embodiment of the present invention. FIG. 13 is a side view of a sample stage for an alternating magnetic force microscope according to a fourth embodiment of the present invention. FIG. 13 is a side view showing a modified example of the sample stage for the alternating magnetic force microscope. FIG. 13 is a side view showing a modified example of the sample stage for the alternating magnetic force microscope. FIG. 2 is a schematic diagram of a system for measuring magnetic flux density in an embodiment. 1 is a graph showing the results of line profiles of each sample stage for an alternating magnetic force microscope in an example. 1 shows a graph of the frequency characteristics of each alternating magnetic force microscope sample stage in the examples.

The following describes a sample stage for an alternating magnetic force microscope according to one embodiment of the present invention with reference to the drawings. FIG. 1 is a perspective view of a sample stage 1 for an alternating magnetic force microscope according to a first embodiment of the present invention. FIG. 2 is a perspective view of a housing 10 in this embodiment. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 1. Note that the dimensions and ratios of each component in the figures do not represent the actual dimensions and ratios of each component.

First Embodiment
As shown in FIG. 1, a sample stage 1 for an alternating magnetic force microscope according to this embodiment includes a housing 10 and a coil 20.

As shown in FIG. 2, the housing 10 has a cylindrical portion 11, a first flange portion 12 disposed at one axial end of the cylindrical portion 11, and a second flange portion 13 disposed on the opposite side to the one end.

As shown in FIG. 3, the cylindrical portion 11 is hollow, and the cross section perpendicular to the axial direction of the cylindrical portion 11 has a circular shape. A conducting wire is wound around the outer circumferential surface of the cylindrical portion 11 to form the coil 20.

A first flange portion 12 is disposed at one axial end of the cylindrical portion 11. The outer surface 121 of the first flange portion 12 is flat. The outer surface 121 is the surface of the first flange portion 12 opposite to the surface connected to the cylindrical portion 11. Because the outer surface 121 is flat, a sample to be observed by the alternating magnetic force microscope can be disposed thereon. In addition, because the outer surface 121 is flat, the distance between the probe of the alternating magnetic force microscope and the sample is constant, and excellent analytical accuracy can be obtained. The thickness (axial length) of the first flange portion 12 is, for example, 2 mm or less.

As shown in FIG. 2, the second flange portion 13 is disposed on the opposite side of the axial end of the tube portion 11 from the end where the first flange portion 12 is disposed. The second flange portion 13 is disposed in contact with the stage of an alternating magnetic force microscope when used. Therefore, in the second flange portion 13 in this embodiment, the outer surface 131, which is the surface of the second flange portion 13 opposite the surface connected to the tube portion 11, is flat. In addition, the second flange portion 13 may have a notch 132 for pulling out both ends of the conductor that constitutes the coil 20, as shown in FIG. 2.

The housing 10 is made of a non-magnetic material. Examples of non-magnetic materials that make up the housing 10 include pure aluminum, aluminum alloys, polyacetal resins, and polymethyl methacrylate resins. If the housing 10 is made of a metal that mainly contains aluminum (pure aluminum, aluminum alloys), it will be lightweight and strong. Therefore, it is preferable to use a metal that mainly contains aluminum for the housing 10. In addition, polyacetal resin has excellent insulating properties, so the generation of eddy currents when an alternating magnetic field is generated is suppressed. Therefore, when a high-frequency current is passed through the coil 20, the strength of the magnetic field near the probe can be increased. Furthermore, if the housing 10 is made of polyacetal resin, it is possible to reduce the weight while maintaining the magnetic field strength. Therefore, it is more preferable to use polyacetal resin for the housing 10.

The coil 20 is formed by winding a conductor around the tube portion 11. Any known conductor may be used, for example, enameled wire. The number of turns of the coil 20 may be determined according to the required magnetic field strength, and may be, for example, 250 to 500.

The sample stage 1 for the alternating magnetic force microscope is placed on the stage of a known alternating magnetic force microscope for use. This allows the distance from the source of the alternating magnetic field to the probe of the alternating magnetic force microscope to be shortened. This therefore makes it possible to suppress attenuation of the intensity of the alternating magnetic field more than ever before, and also to improve the perpendicularity of the magnetic field near the probe. As a result, the spatial resolution of the alternating magnetic force microscope can be improved.

In addition, since the alternating magnetic force microscope sample stage 1 is used by being placed on the stage of a known alternating magnetic force microscope, the alternating magnetic force microscope sample stage 1 is a size that can be placed on the stage of a known alternating magnetic force microscope, for example, its diameter is 25 mm to 37 mm, and its height (axial length) is 15 mm to 22 mm. According to the alternating magnetic force microscope sample stage 1, as described above, the magnetic field strength near the probe can be improved by shortening the distance from the source of the alternating magnetic field to the probe of the alternating magnetic force microscope. Therefore, since the magnetic field strength required for observation can be obtained with a smaller current than that of a conventional alternating magnetic field source, the size of the alternating magnetic force microscope sample stage 1 that generates the alternating magnetic field can be made smaller than that of a conventional alternating magnetic field source. For example, the low-field alternating magnetic field source described in Non-Patent Document 1 has a diameter of 40 mm and a height of 28 mm, but to obtain a magnetic field strength similar to that produced by this alternating magnetic field source, the sample stage 1 for the alternating magnetic force microscope only needs to be approximately 37 mm in diameter and 22 mm in height.

As described above, the sample stage 1 for the alternating magnetic force microscope can shorten the distance from the source of the alternating magnetic field to the probe of the alternating magnetic force microscope, so that even with a small current, the strength of the magnetic field near the probe of the alternating magnetic force microscope can be increased. Therefore, with the sample stage 1 for the alternating magnetic force microscope according to this embodiment, the magnetic field strength can be controlled by changing the magnitude of the current.

Second Embodiment
Next, a sample stage 1A for an alternating magnetic force microscope according to a second embodiment of the present invention will be described with reference to Figures 4 and 5. Figure 4 is a perspective view of a sample stage for an alternating magnetic force microscope according to the second embodiment of the present invention. Figure 5 is a cross-sectional view taken along line IV-IV in Figure 4.

As shown in Figures 4 and 5, the sample stage 1A for alternating magnetic force microscopes according to this embodiment comprises a housing 10, a coil 20, and a cover 30. The sample stage 1A for alternating magnetic force microscopes differs from the sample stage 1 for alternating magnetic force microscopes in that it comprises a cover 30, but the housing 10 and the coil 20 are the same as those in the first embodiment, so a description of these will be omitted here. The cover 30 will be described below.

The cover 30 is a ring-shaped cover formed by stacking electromagnetic steel sheets in the axial direction. As shown in FIG. 5, the cover 30 is disposed on the outer periphery of the first flange portion 12 and the coil 20. The cover 30 reduces leakage magnetic flux and increases magnetic flux density. In addition, because the cover 30 is a laminate of electromagnetic steel sheets, eddy currents generated in the cover 30 are reduced, and eddy current loss can be suppressed.

The electromagnetic steel sheets that make up the cover 30 are not particularly limited and may be any known type. The number of laminated layers of the electromagnetic steel sheets may also be determined according to the magnitude of the current flowing through the coil 20.

Third Embodiment
Next, a sample stage 1B for an alternating magnetic force microscope according to a third embodiment of the present invention will be described with reference to Fig. 6. Fig. 6 is a cross-sectional view of a cross section including the central axis of the sample stage 1B for an alternating magnetic force microscope according to this embodiment.

As shown in FIG. 6, the sample stage 1B for alternating magnetic force microscopes according to this embodiment includes a housing 10, a coil 20, and a magnetic core 40. The sample stage 1B for alternating magnetic force microscopes differs from the sample stage 1 for alternating magnetic force microscopes in that it includes a magnetic core 40, but the housing 10 and the coil 20 are the same as those in the first embodiment, so a description of these will be omitted here. The magnetic core 40 will be described below.

As shown in FIG. 6, the magnetic core 40 is housed inside the tube portion 11. The magnetic core 40 is made of a material with high magnetic permeability, such as pure iron, an iron-based alloy, or a ferrite or permalloy whose main component is iron oxide. The magnetic core 40 may be a laminated core in which electromagnetic steel sheets are laminated, or an amorphous core. The magnetic core 40 can increase the magnetic flux density and improve the verticality of the magnetic field.

Fourth Embodiment
Next, a sample stage 1C for an alternating magnetic force microscope according to a fourth embodiment of the present invention will be described with reference to Fig. 7. Fig. 7 is a side view of the sample stage 1C for an alternating magnetic force microscope according to this embodiment.

As shown in FIG. 7, the sample stage 1C for alternating magnetic force microscopes according to this embodiment includes a housing 10, a coil 20, and a fixed portion 50. The sample stage 1C for alternating magnetic force microscopes differs from the sample stage 1 for alternating magnetic force microscopes in that it includes a fixed portion 50, but the housing 10 and the coil 20 are the same as those in the first embodiment, so a description of these will be omitted here. The fixed portion 50 will be described below.

As shown in FIG. 7, the fixing portion 50 is a threaded portion extending from the outer surface 131 of the second flange portion 13 in the housing 10. When a threaded hole is provided in the stage of the alternating magnetic force microscope, the fixing portion 50 fits into the threaded hole and the alternating magnetic force microscope sample stage 1C is fixed to the stage of the alternating magnetic force microscope. This allows the alternating magnetic force microscope sample stage 1C to be more firmly fixed to the stage.

Up to this point, the present invention has been described with reference to embodiments, but the present invention is not limited to the above-mentioned embodiments. For example, the configurations of the above-mentioned embodiments may be combined. In detail, the alternating magnetic force microscope sample stage according to the present invention may include two or more of the cover 30, the magnetic core 40, and the fixed portion 50. From the viewpoint of achieving a greater magnetic field strength and a more uniform magnetic field perpendicularity, it is preferable that the alternating magnetic force microscope sample stage includes the cover 30 and the magnetic core 40.

The first flange portion 12 may have a hole communicating with the tubular portion 11, as shown in FIG. 8, for example, and the lid 122 may be fitted into the hole. In this case, the outer surface 121 of the first flange portion 12 and the outer surface of the lid 122 are configured to be flat. The magnetic core 40 can be inserted into and removed from the interior of the tubular portion 11 through the hole communicating with the tubular portion 11.

In the first embodiment and the like described above, the cross-section perpendicular to the axial direction of the tube portion 11 has a circular shape, but this shape is not limited to a circle and may be various shapes such as a rectangle. From the viewpoint of realizing uniform magnetic field verticality, it is preferable that the cross-section perpendicular to the axial direction of the tube portion 11 has a circular shape in order to form a coil 20 in which the conductor wire is wound uniformly in the cross-section perpendicular to the axial direction.

The space inside the tube portion 11 may extend to either the first flange portion 12 or the second flange portion 13. In other words, at least one of the first flange portion 12 or the second flange portion 13 may have a recess connected to the space inside the tube portion 11. For example, in the alternating magnetic force microscope sample stage 1E shown in FIG. 9, the first flange portion 12 is provided with a recess 123 connected to the space inside the tube portion 11, and the second flange portion 13 is provided with a recess 133 connected to the space inside the tube portion 11. This allows a magnetic core 40 that is longer than the height (axial length) of the coil 20 to be arranged inside the coil 20, thereby further improving the verticality of the magnetic field.

In addition, in the first embodiment and the like described above, the tube portion 11 is hollow, but the tube portion 11 may be solid. If the tube portion 11 is solid, the housing 10 can be manufactured more easily.

The present invention will be described in detail below with reference to examples. However, the present invention is not limited to these examples.

Example 1
Sample stages for alternating magnetic force microscopes (inventive examples 1 to 4) were produced. In inventive example 1, an alternating magnetic force microscope sample stage was used that had a housing and a coil as shown in FIG. 3. Specifically, the diameter of the cylindrical portion was 10 mm, and the height of the alternating magnetic force microscope sample stage was 22 mm. In inventive example 2, a magnetic core (product number I-93K) manufactured by JFE Ferrite Corporation, having a diameter of 8 mm and a height of 20 mm, was inserted inside the cylindrical portion of the housing of inventive example 1. In inventive example 3, a cover was provided on the outer periphery of the first flange portion and the coil in the alternating magnetic force microscope sample stage of inventive example 1. The cover was made by laminating 66 sheets of electromagnetic steel plate (manufactured by Denki Shizai Co., Ltd., product number 30ZH105) having a thickness of 0.3 mm. The outer diameter of the cover was 37 mm, and the thickness was mm. In Inventive Example 4, a magnetic core similar to that in Inventive Example 2 was inserted inside the cylindrical portion of the alternating magnetic force microscope sample stage in Inventive Example 3. The housings in Inventive Examples 1 to 4 were made of aluminum. In Inventive Examples 1 to 4, an enameled wire with a diameter of 0.6 mm was used as the conductor, and the coil was wound 485 times around the cylindrical portion.

The magnetic field uniformity of each of the alternating magnetic force microscope sample stages of the present invention 1 to 4 was evaluated using the magnetic field measurement system shown in FIG. 10. FIG. 10 is a schematic diagram of the magnetic field measurement system in the embodiment. The distance from the outer surface of the first flange of the alternating magnetic force microscope sample stage to the Hall sensor was set to 2 mm. This distance corresponds to the distance from the upper surface of the stage on which the sample is placed to the probe, which can be taken in the alternating magnetic force microscope. The current flowing through the coil was amplified by connecting a function generator (WF1974, manufactured by NF Corporation) as a signal source to a high-speed bipolar power supply (BA4850, manufactured by NF Corporation). The magnitude of the conducting current was set to 0.8 A _PP , the magnetic field was detected by the Hall sensor, and the phase was detected by the lock-in amplifier. The lock-in amplifier output a signal related to the magnetic field detected by the Hall sensor, and PC2 obtained a line profile based on the signal. During the measurement, the current between the alternating magnetic force microscope sample stage and the power supply and the offset were controlled to be constant using a current-voltage conversion circuit and system development software (LabVIEW, National Instruments).

The line profile was obtained by setting the modulation frequency to 90 Hz and scanning the Hall sensor in a range of ±40 mm (0 to 80 mm) from the center of the sample stage for the alternating magnetic force microscope.

The line profiles obtained for each example are shown in Figure 11. As shown in Figure 11, a high-strength magnetic field was obtained in all of Examples 1 to 4 of the present invention. In addition, the observation range of the alternating magnetic force microscope was approximately 0.1 mm square, and the strength of the magnetic field decayed continuously over space, so that, as shown in Figure 11, good magnetic field perpendicularity was obtained in the observation range using the alternating magnetic force microscope.

Example 2
As Inventive Example 5, a case made of polyacetal resin was prepared, and a sample stage for an alternating magnetic force microscope was otherwise fabricated similarly to Inventive Example 4. Using the magnetic field measurement system shown in Fig. 10, the frequency characteristics of the sample stages for an alternating magnetic force microscope of Inventive Examples 4 and 5 were evaluated. The frequency characteristics were obtained based on the signal output by the lock-in amplifier by fixing the Hall sensor directly above the central axis of the sample stage for an alternating magnetic force microscope and performing a sweep measurement from 10 Hz to 1500 Hz.

Figure 12 shows a graph of the frequency characteristics of each alternating magnetic force microscope sample stage. As shown in Figure 12, it was found that Example 5 of the present invention, which is an example of an alternating magnetic force microscope sample stage having a polyacetal resin housing, maintains a large magnetic flux density even in the high frequency range compared to Example 4 of the present invention. This is thought to be because eddy currents are suppressed compared to Example 4 of the present invention, which is an example of an alternating magnetic force microscope sample stage having an aluminum housing.

REFERENCE SIGNS LIST 1, 1A, 1B, 1C, 1D, 1E Sample stage for alternating magnetic force microscope 10 Housing 11 Cylindrical portion 12 First flange portion 13 Second flange portion 20 Coil 30 Cover 40 Magnetic core 121 Outer surface of first flange portion 122 Lid 123 Recess 131 Outer surface of second flange portion 132 Notch 133 Recess

Claims (7)

a housing having a cylindrical portion, a first flange portion disposed at one end of the cylindrical portion, and a second flange portion disposed on an opposite side to the one end;
a coil formed by winding a conductive wire around the cylindrical portion,
A sample stage for an alternating magnetic force microscope, wherein the outer surface of the first flange portion is flat. The sample stage for an alternating magnetic force microscope according to claim 1, further comprising a magnetic core housed inside the cylindrical portion. The sample stage for an alternating magnetic force microscope according to claim 1 or 2, further comprising a ring-shaped cover made of a magnetic material and arranged around the first flange portion and the outer periphery of the conductor. The sample stage for an alternating magnetic force microscope according to claim 1 or 2, wherein the housing is made of a metal containing mainly aluminum. The sample stage for an alternating magnetic force microscope according to claim 1 or 2, wherein the housing is made of polyacetal resin. The alternating magnetic force microscope sample stage according to claim 1 or 2, wherein the second flange portion has a fixing portion for fixing the alternating magnetic force microscope sample stage. The sample stage for an alternating magnetic force microscope according to claim 1 or 2, having a diameter of 25 mm or more and 37 mm or less.

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