JPH01195354A - Electron spin resonance microscope - Google Patents

Abstract

PURPOSE:To derive a two-dimensional electron spin distribution of a sample by providing a local magnetic field modulation coil so as to be opposed to the sample and scanning two-dimensionally the sample or a modulation coil by using said coil. CONSTITUTION:By an XY stage 13, a sample 23 is scanned in the X and Y directions and a magnetic field sweep is executed in each position, and by a modulation coil 25, a magnetic field modulation is executed by, for instance, 100kHz and an absorbing signal by an electron spin resonance is detected. A detecting signal is fetched in a form that a carrier of, for instance, 9GHz has been modulated by 100kHz from a directional coupler 31, detected by a detector 33, and also, only a 100kHz component is detected by a narrow-band amplifier 35. By bringing said component to phase detection by 100kHz from a modulating signal generator 27, a resonance signal by an electron spin of a part opposed to a modulation coil is detected as a differential waveform. In such a way, a two-dimensional electron spin distribution of the sample can be derived.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electron spin resonance (ESR) microscope capable of detecting a two-dimensional distribution of electron spins.

[Conventional technology]

Recently, magnetic co-■! The development of MHI imaging (MRr) is broadly divided into nuclear magnetic resonance (NMR) imaging and electron spin resonance (ESR) imaging, both of which involve superimposing a magnetic field gradient on a uniform static magnetic field. Obtain NMR or ESR images. Currently,
NMR imaging devices mainly aimed at the human body have been put into practical use for medical purposes. For medical purposes, a resolution on the order of milliseconds is sufficient, but if this resolution is further increased, it will be possible to observe MHI images of biological cells, which will open the door to use as an NMRam mirror or an ESR microscope. development is underway.

[Problem to be solved by the invention]

In order to improve resolution and performance as a W4 microscope, it is necessary to increase the magnetic field gradient compared to medical use, and in the case of an NMR microscope,
To obtain a spatial resolution of about 10 μm, several tens of Gauss/
A magnetic field gradient of the order of cI11 is required. However, in ESR, the linewidth of the resonance signal is usually wide, ranging from several Gauss to several tens of Gauss, so a high magnetic field gradient is required. For example, to obtain a resolution of 10 μm, even if the linewidth is 2 Gauss, A magnetic field gradient of approximately 1000 Gauss/cm is required, and it is difficult to provide such a large magnetic field gradient on the Z-axis using a method similar to NMR, making it difficult to measure the two-dimensional distribution of spins.

The present invention is intended to solve the above problems, and is characterized by providing an electron spin resonance microscope that makes it possible to obtain a two-dimensional spin distribution by applying a local magnetic field to a sample.

[Means to solve the problem]

To this end, the electron spin resonance microscope of the present invention applies a microwave magnetic field to a sample placed in a sweepable static magnetic field, and detects signals based on electron spin resonance. a local magnetic field modulation coil disposed facing the surface; a narrowband amplifier that passes a signal of the local magnetic field modulation frequency among the detection signals; and a phase detector that phase-detects the output of the narrowband amplifier using the magnetic field modulation signal;
It is characterized by comprising a scanning means for two-dimensionally scanning the sample or the local magnetic field modulation coil, and detecting the two-dimensional electron spin distribution of the sample by two-dimensionally scanning the sample or the local magnetic field modulation coil.

[Effect]

In the electron spin resonance microscope of the present invention, a local magnetic field modulation coil is provided facing the sample, a modulation signal is supplied to the modulation coil to locally modulate the magnetic field, and the detected signal is modulated by phase detection with the modulation signal. By detecting only the magnetic field-modulated resonance signal at a position facing the coil and two-dimensionally scanning the sample or the modulation coil, it is possible to determine the two-dimensional electron spin distribution of the sample.

(Example〕 Examples will be described below with reference to the drawings.

FIG. 1 is a diagram showing the configuration of an electron spin resonance microscope according to the present invention, FIG. 2 is a diagram showing a local magnetic field modulation coil and a sample according to the present invention, and FIG. 3 is a diagram showing detection signal waveforms at various parts. In the figure,
11 is a control device, 13 is an XY stage, 15 is an excitation power source, 17 is a magnetic field generator, 19 is a cavity resonator, 21 is a rod, 23 is a sample, 25 is a local magnetic field modulation coil, 27 is a modulation signal generator, 29 is a microwave oscillator, 31 is a directional coupler, 33 is a detector, 35 is a narrowband amplifier, 37 is a phase detector, 39 is a recorder, 41.43 is a quartz tube, 45 is a sample holder, 47 is a coil It is a holder.

In the figure, a sample 23 supported by a sample holder 45 is placed in a static magnetic field generated by a magnetic field generator 17,
The XY stage 13 whose drive is controlled by the control device 11 scans in the X direction and the Y direction via the rod 21 .

A modulation coil 39 held by a coil holder is arranged facing the sample, and a local magnetic field modulation signal of, for example, 100 kHz is supplied from a modulation signal generator 27. The magnetic field generator 17 can be swept by the excitation power source 15 to change the magnetic field strength. Also, cavity resonator 1
9 is supplied with microwaves of, for example, 9 GHz from a microwave oscillator 29, and the reflected waves generated when the matching of the resonator 19 is broken due to the electron pin resonance of the sample are detected via the directional coupler 31. It is configured to be taken out in the direction of the container 33 and detected.

In this configuration, the sample 23 is scanned in the X and Y directions by the XY stage 13, the magnetic field is swept at each position, and the modulation coil 39 modulates the magnetic field at 100 kHz to detect an absorption signal due to electron spin resonance. .

The detection signal at this time is, for example, as shown in FIG. 3(a) from the directional coupler 31, the 9 GHz carrier is
It is extracted in the form modulated at kHz, and this is sent to the detector 3.
3, a signal as shown in FIG. 3(b) is detected. and a narrowband amplifier 35 that passes 100 kHz.
As shown in FIG. 3(C), only the 100KHz component is detected, and this is
By performing phase detection at Hz, a resonance signal due to the electron spin in the portion facing the modulation coil is detected as a differential waveform as shown in FIG. 3(d).

In addition, when multiple types of components such as Fe, Mn, and Cu are present at the same site, they are observed at each position on the sample surface with a predetermined spectral shift as shown in Figure 4 (a). By integrating this, the absorption waveform is obtained as shown in Figure 4 (b), and the l? of the spin for each component at each position is obtained. 2 ffi can be detected.

In the above explanation, the magnetic field strength is swept at each position,
The two-dimensional distribution of spins was obtained by detecting all the components contained therein, but by fixing the magnetic field strength to a value where the peak of a specific component appears and scanning in the X and Y directions, If the distribution is determined, a two-dimensional distribution of only the specific component can be determined.

Figure 5 shows a test sample with a pinhole made with a needle, filled with fine particles of DPPH (diphenylvicrylhydrazyl), and the surface covered with a 10 μm Teflon film to prevent the fine particles of DPPH from falling. This figure shows the case where the sample is attached to a sample holder and set in a cavity resonator, and the sample is scanned in the X and Y directions with the local magnetic field modulation coil according to the present invention facing each other. FIG. 2B is a cross-sectional view of FIG. 2B, and FIG. The D P P H spot used had a diameter of 170 microns, and the modulation coil had a radius of 120 microns and 7 turns.

The broken line in Figure 5 (b) shows the case where the phase of the current supplied to the modulation coil is changed by 180 degrees, and it can be seen that if the phase of the current supplied to the local magnetic field modulation coil is changed by 180 degrees, a spectrum with reversed polarity can be obtained. It can be seen that the detected signal is due to local magnetic field modulation.

Also, as shown in Fig. 5(c), when the DPPH sub-board is at the center of the modulation coil, it becomes maximum, and 'D P P
The H spot became smaller as it moved away from the center of the modulation coil, and the half width of the peak value was 270 μm. It can be seen that this value is approximately equal to the diameter of the modulation coil and therefore the resolution is equal to the diameter of the modulation coil.

Figure 6 (a) shows the pattern of three spots of DPPH in a sample, and the two spots shown in Figure 6 (b) are obtained for such a sample by the local magnetic field method according to the present invention.
A dimensional spin distribution image, a perspective image as shown in FIG. 6 (c), was obtained.

In Fig. 7, the modulation coil diameter is 2r, &i diameter is 23. It is a diagram showing the magnetic field strength around the coil calculated by setting a/r to 0.25 and the number of turns to 7, where Z=(l is taken from the sample surface.

From FIG. 7, when ρ<Q, 5r, the magnetic field strength at the sample surface is constant, and it decreases rapidly near ρ=r. and E
When the modulation width is smaller than the linewidth of the signal, the SR intensity changes f
Since it is proportional to the IvA field strength, it can be seen that the resolution is equal to the diameter of the modulation coil, which is shown in Figure 5 (c).
This is consistent with the results of Also, when ρ>1.25r, the magnetic field strength becomes negative and the phase is reversed to ρ<1.25r, which is due to D
This causes the PPH spot to be detected as a weak phase inversion signal when it moves away from the coil center.

It can also be seen that the magnetic field strength rapidly decreases in the X direction, the sample detection accuracy is less than the diameter of the modulation coil, and only the sample surface can be detected.

In the above embodiment, the sample was scanned two-dimensionally, but it goes without saying that the sample may be fixed and the modulation coil scanned two-dimensionally.

〔Effect of the invention〕

As described above, according to the present invention, by scanning the sample or the modulation coil two-dimensionally using the local magnetic field modulation coil, it is possible to obtain the two-dimensional electron spin distribution of the sample with a resolution determined by the diameter of the modulation coil. This makes it possible to selectively detect only different types of radicals.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an electron spin resonance microscope according to the present invention, FIG. 2 is a diagram showing a local magnetic field modulation coil and a sample according to the present invention, FIG. 3 is a diagram showing detection signal waveforms at various parts, and FIG.
Figure 5 shows the spectral waveform, Figure 5 shows the test sample and its detection results, Figure 6 shows the two-dimensional DPP H spot pattern and the detection results, and Figure 7 shows the modulation coil and its surroundings. FIG. 3 is a diagram showing magnetic field strength. 11...control device, 13...XY stage, 15.
...Excitation power supply, 17...Magnetic field generator, 19...
Cavity resonator, 23... Sample, 25... Local magnetic field modulation coil, 27... Modulation signal generator, 29... High frequency oscillator, 35... Narrowband amplifier, 37... Phase detector . Applicant JEOL Co., Ltd. Agent Patent Attorney Masanobu Hirukawa (4 others) Figure 1 Figure 2 6 e E- Intensity +/+p

Claims (1)

[Claims] In an electron spin resonance apparatus that applies a microwave magnetic field to a sample placed in a sweepable static magnetic field and detects a signal based on electron spin resonance, a local magnetic field modulation coil and a local magnetic field modulation coil placed opposite the sample surface are used. , a narrowband amplifier that passes a signal having a local magnetic field modulation frequency among the detection signals;
It is equipped with a phase detector that detects the phase of the narrowband amplifier output using a magnetic field modulation signal, and a scanning means that scans the sample or the local magnetic field modulation coil two-dimensionally. An electron spin resonance microscope characterized by detecting dimensional electron spin distribution.