Magnetic field value measuring device and method for measuring magnetic field value

Patent metadata

Field	Value
Publication number	US-2016109478-A1
Application number	US-201414777667-A
Country	US
Kind code	A1
Filing date	Mar 28, 2014
Priority date	Mar 28, 2013
Publication date	Apr 21, 2016
Grant date	—

Abstract

A magnetic field measuring device including: a vibrational probe unit having a probe that includes one or more material(s) whose intensity of magnetization is proportionate to an external magnetic field, a mechanical vibration source for the probe; a vibration detector detecting a vibration frequency and amplitude of the probe; an alternating-current magnetic field generator applying to the probe an alternating-current magnetic field; a direct-current external magnetic field generator applying a direct-current external magnetic field to the probe; a frequency modulation detector detecting frequency modulation occurring to the mechanical vibration of the probe; a direct-current external magnetic field controller adjusting the intensity of the direct-current external magnetic field applied to the probe; and a direct-current magnetic field determination unit determining a value of the direct-current magnetic field originating from a specimen.

First claim

1 . A magnetic field measuring device which detects a direct-current magnetic field originating from a specimen, the device comprising:
a vibrational probe unit comprising a probe, the probe comprising one or more material whose intensity of magnetization is proportionate to an external magnetic field; a mechanical vibration source mechanically oscillating the probe; a vibration detector detecting a mechanical vibration frequency of the probe and a mechanical vibration amplitude of the probe; an alternating-current magnetic field generator applying an alternating-current magnetic field to the probe, the alternating magnetic field having a frequency different from the mechanical vibration frequency of the probe and having a nonzero gradient in a direction of the mechanical vibration of the probe; a direct-current external magnetic field generator applying to the probe a direct-current external magnetic field in the direction of the mechanical vibration of the probe; a frequency modulation detector detecting frequency modulation occurring in the mechanical vibration of the probe from the mechanical vibration frequency detected by the vibration detector: a direct-current external magnetic field adjuster adjusting intensity of the direct-current external magnetic field in the direction of the mechanical vibration of the probe applied by the direct-current external magnetic field generator to the probe; and a direct-current magnetic field determination unit determining a value of the direct-current magnetic field in the direction of the mechanical vibration of the probe originating from the specimen, based on an output value of the direct-current external magnetic field generator when intensity of the frequency modulation takes a minimum value or on an expected output value of the direct-current external magnetic field generator when the intensity of the frequency modulation is expected to take a minimum value.

2 . The magnetic field measuring device according to claim 1 ,
wherein the direct-current external magnetic field adjuster adjusts the direct-current external magnetic field such that the direct-current external magnetic field totally cancels the direct-current magnetic field.

3 . The magnetic field measuring device according to claim 1 ,
wherein the direct-current external magnetic field adjuster adjusts the direct-current external magnetic field such that the direct-current external magnetic field partly cancels the direct-current magnetic field.

4 . The magnetic field measuring device according to claim 1 ,
wherein the alternating-current magnetic field generator comprises an electromagnetic coil.

5 . The magnetic field measuring device according to claim 1 ,
wherein the alternating-current agnetic field generator comprises two or more electromagnetic coils; the two or more electromagnetic coils generate a plurality of magnetic fields in directions such that the plurality of magnetic fields are mutually cancelled at the tip of the probe, such that the alternating-current magnetic field generator generates a magnetic field having a position where magnetic field amplitude is zero; and a magnetic field gradient of the magnetic field generated by the alternating-current magnetic field generator at the position where the magnetic field amplitude is zero is greater than any magnetic field gradient of the magnetic field generated by each single electromagnetic coil of the two or more electromagnetic coils.

6 . The magnetic field measuring device according to claim 1 ,
wherein the direct-current external magnetic field generator comprises an electromagnetic coil which applies a magnetic field to the probe; and the direct-current external magnetic field adjuster comprises an electric current adjuster.

7 . The magnetic field measuring device according to claim 1 , claim further comprising:
a mechanism scanning a surface of the specimen one-dimensionally, two-dimensionally, or three-dimensionally by means of the probe.

8 . A method for measuring a direct-current magnetic field originating from a specimen by means of a vibrational probe unit comprising a probe, the probe comprising a one or more magnetic material whose intensity of magnetization is proportionate to intensity of an external magnetic field, the method comprising the steps of:
mechanically oscillating the probe; applying an alternating-current magnetic field and a direct-current external magnetic field to the probe, wherein the alternating magnetic field has a frequency different from a mechanical vibration frequency of the probe and has a nonzero gradient in a direction of the mechanical vibration of the probe, and wherein the direct-current external magnetic field is applied in the direction of the mechanical vibration of the probe and is applied in a direction in which the direct-current magnetic field originating from the specimen is cancelled; detecting frequency modulation which occurs in the mechanical vibration of the probe; adjusting intensity of the direct-current external magnetic field applied to the probe in the direction of the vibration, based on detection result of the frequency modulation; determining a value of the direct-current magnetic field in the direction of the vibration originating from the specimen, based on a value of the direct-current external magnetic field when the frequency modulation does not occur or when intensity of the frequency modulation takes a minimum value, or on an expected value of the direct-current external magnetic field when the intensity of the frequency modulation is expected to take a minimum value.

9 . The method for measuring the magnetic field according to claim 8 , comprising the step of:
adjusting the direct-current external magnetic field such that the direct-current external magnetic field totally cancels the direct-current magnetic field.

10 . The method for measuring the magnetic field according to claim 8 , comprising the steps of:
adjusting the direct-current external magnetic field such that the direct-current external magnetic field partly cancels the direct-current magnetic field; and determining the value of the direct-current magnetic field in the direction of the vibration originating from the specimen, based on at least two values of the direct-current external magnetic field and intensities of frequency modulation corresponding to the at least two values of the direct-current external magnetic field.

11 . The method for measuring the magnetic field according to claim 8 , comprising the step of:
either (a) calibrating the alternating-current magnetic field such that intensity of the frequency modulation becomes zero, or (b) calibrating the alternating-current magnetic field such that the intensity of the frequency modulation gets closer to zero.

12 . The method for measuring the magnetic field according to claim 8 , comprising the step of:
scanning a surface of the specimen one-dimensionally, two-dimensionally, or three-dimensionally by means of the probe.

Assignees

• Univ Akita
• Univ Osaka

Inventors

• Saito Hitoshi
• Yoshimura Satoru
• Kinoshita Yukinori
• NOMURA Hikaru
• Nakatani Ryoichi

Classifications

• G01Q60/54

  Probes, their manufacture, or their related instrumentation, e.g. holders · CPC title

• G01Q60/56

  Probes with magnetic coating · CPC title

• G01Q60/50

  MFM [Magnetic Force Microscopy] or apparatus therefor, e.g. MFM probes · CPC title

• G01Q60/52 Primary

  Resonance · CPC title