JP2006038500A - High magnetic field/high frequency electron spin resonance (esr) measuring apparatus by pulse magnetic field applied with magnetization detection by cantilever - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem wherein the formation of high frequency is limited because the high frequency depends on a size of a cavity resonator, in a high-frequency electron spin resonance (ESR) apparatus. <P>SOLUTION: In the present invention, a sample 2 is attached to a tip of a cantilever 4, a strong magnetic field is generated by a pulse magnetic field, and a deflection displacement due to moment force acting on the cantilever is measured by magnetization generated with resonance of an unpaired electron in the sample, resulting from irradiation of an electromagnetic wave. A deflection change of the cantilever is detected by an instrument such as a strain gage and an optical lever to detect a physical property by electron spin resonance. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for measuring electron spin resonance (ESR) due to unpaired electrons present in a sample such as a paramagnetic substance and a ferromagnetic substance, and a measuring apparatus therefor. More specifically, the present invention relates to a method for measuring electron spin resonance characterized by detecting a change in magnetic torque of a cantilever due to electron spin resonance absorption of a sample attached to the cantilever. According to the measurement method of the present invention, it is possible to detect and measure electron spins in a minute region with high sensitivity using simple equipment.

  Normally, the orbit of an atom or molecule contains a pair of two electrons whose rotations (spins) are opposite to each other (and thus the directions of magnetic moments are opposite), but they do not form a pair (" Substances such as transition metals and radicals (free radicals) having “unpaired electrons”) are divided into two energy states depending on whether the direction of the magnetic moment is parallel or antiparallel in a stationary magnetic field. The phenomenon of absorbing electromagnetic waves corresponding to this energy difference is “electron spin resonance (ESR)”. When an unpaired electron having a spin quantum number S is placed in a stationary magnetic field, the energy level is Zeeman-divided into 2S + 1 by the interaction between the magnetic field created by the spin of the unpaired electron and the external magnetic field. Electron spin resonance is a phenomenon where absorption occurs resonantly when an electromagnetic wave equal to the energy difference between adjacent levels is applied, and its measurement is conventionally performed by measuring the absorption or emission of an electromagnetic wave. ing.

By measuring electron spin resonance, it is possible to detect only substances having unpaired electrons with high sensitivity without decomposing the sample. Therefore, this measurement is frequently used for the analysis of ferromagnets and paramagnetic substances. ing.
A conventionally used electron spin resonance measuring apparatus is one in which electromagnetic waves are incident on a cavity resonator containing a measurement sample and the reflected electromagnetic waves are monitored (Patent Document 1). The cavity resonator and the sample constitute a kind of resonance circuit for electromagnetic waves. Microwaves are usually used for the frequency of electromagnetic waves, and in measurement, the sample is placed in a resonator and the magnetic field is swept while microwaves with a constant frequency are applied, and the absorption spectrum is acquired and analyzed. .

ESR measurement is considered to be a cause of research on physical properties of magnetic materials, semiconductors, polymer compounds, etc., detection of presence / absence of radicals and trace elements in metal compounds, carcinogenesis, arteriosclerosis, aging, etc. It is also used for measuring active oxygen and free radicals in the body.
As the frequency, the 10 GHz band (magnetic field of about 0.3 Tesla or less) is most used in terms of sensitivity and simplicity. However, in recent years, a superconducting magnetic field is used for the W band (95 GHz band), higher frequency millimeter waves, submillimeters. Waves are attracting attention from the standpoints of high sensitivity and sample miniaturization. In general, an advantage of an ESR device with a high frequency and a high magnetic field is that it is effective for dynamic analysis such as a living body because resolution is improved.

However, in the conventional ESR apparatus, since the frequency depends on the size of the cavity resonator and there is a limit to the increase in the frequency, the measurement sensitivity of electron spin resonance has reached the theoretical limit.
In addition, the conventional ESR apparatus uses a steady magnetic field, and for example, a large-scale facility such as a power source and a cooling facility is required for a high magnetic field of 20 Tesla or higher.

  In addition, a magnetic resonance exchange interaction force microscope that measures the exchange interaction force acting between the probe and the sample by incorporating magnetization reversal / modulation technology by electron spin resonance into an atomic force microscope (AFM). Known (Patent Document 2). This applies electromagnetic force to the probe at the tip of the cantilever facing the sample, generates probe magnetization reversal / modulation action due to resonance, and measures the exchange interaction force acting between the probe and the sample. It is.

  However, the magnetic resonance type exchange interaction force microscope is intended to observe the magnetic structure of the sample surface, and not to observe the electronic state of a minute bulk sample. Further, it has not been known that electron spin resonance itself can be directly observed with high sensitivity by measuring the amount of magnetization reversal of the sample itself with a cantilever and detecting the magnetization reversal with a cantilever.

In addition, it is known that electron spin resonance can be measured with an AFM configuration using a cantilever (Patent Document 3). In this measurement, the AFM atomic force measurement is replaced with the magnetic resonance force measurement, and the spatial resolution is very high, and there is a significance of probing a force different from that of the AFM. Since the configuration of a conventional ESR measurement device that irradiates electromagnetic waves in the millimeter wave region with an oscillator is used, sensitivity is limited.
Further, it has not been known that a change in magnetization due to ESR can be observed as a torque of a cantilever.

JP 05-107327 A JP 2000-180341 A U.S.Patent Patent Number: 5585722 (Embodiment5, FIG.6)

  A conventional ESR apparatus creates a stationary static magnetic field with an electromagnet, causes Zeeman splitting of electrons in a sample, and gives an electromagnetic field matching the energy difference by a micro-transmitter or the like to resonate unpaired electrons. Usually, since a certain electromagnetic wave is given, information on which magnetic field is absorbed becomes information. In an ordinary apparatus, the amount of energy stored in the box of the cavity resonator (container) is lost, that is, the change in the Q value is amplified and detected. However, the size of the container is related to the frequency, and it is necessary to make the container small for high-frequency measurement, and the sample must be smaller than the container so as not to disturb the function of the resonator. Therefore, there is a problem that even if high frequency measurement is attempted to increase the measurement resolution, the high frequency measurement itself is difficult due to the size of the container.

A commonly used X-band ESR apparatus uses a 9 GHz electromagnetic wave, and a resonant magnetic field is only 0.3 T, so a water-cooled steady magnetic field is used. This X-band ESR device uses radio waves, makes use of the fact that the wavelength of electromagnetic waves is on the order of cm, raises the Q value using a cavity resonator, performs lock-in detection by magnetic field modulation, and is limited in principle. Sensitivity (minimum observable electron spin number 10 ¹⁰ ). However, the resolution for discriminating different resonant magnetic fields is low, and the use of a cavity resonator makes it impossible in principle to increase the spatial resolution. With regard to the sensitivity of this X-band ESR apparatus, when a thin film sample such as a spin electronics material is to be measured, the spin number is about 10 ¹⁸ / cm 3 at a film thickness of 1 μm, and the sensitivity is very limited. Therefore, there is a demand for a more sensitive ESR measurement method that can increase the spatial resolution without using a cavity resonator and can selectively measure a limited space.

  On the other hand, in the electron spin resonance, the electronic state is examined through a so-called g value obtained from the resonance. When two resonances having close g values exist, the difference between the resonance magnetic fields increases as the magnetic field increases at a high frequency. Therefore, when the line width is taken into consideration, the separation becomes easy and the resolution becomes high. This is an advantage common to magnetic resonance. In nuclear magnetic resonance, 1 GHz nuclear magnetic resonance has been developed for high-resolution measurement of proteins. In the case of electron spin resonance, the mass of electrons is about 2000 times lighter than that of the nucleus, and measurement using electromagnetic waves close to light is required instead of radio waves. Thus, when measuring with the electromagnetic wave close | similar to light, the wavelength of electromagnetic waves is short from a mini wave to a submillimeter wave (THz light), and it becomes impossible to use a cavity resonator.

  Recently, research on nanomaterials represented by a group of substances such as carbon nanotubes, nanowires, and nanodots has been actively conducted. However, since such a system is very small and minute, its electron spin resonance. Measurement requires high sensitivity and high spatial resolution. In addition, organic crystals and biological materials can be obtained in trace amounts of mg or less, even if they are not nano-sized, and observation of such a minute amount of electron spin resonance is very difficult with X-band ESR. It was.

  Further, in high frequency / high magnetic field measurement, the transmittance was conventionally observed with an InSb (indium antimony) detector to detect the change, but sensitivity cannot be obtained without a certain amount of sample. There was a problem. Furthermore, in the case of an InSb detector, electron-hole pairs are generated with thermal energy even at room temperature, so there is a lot of measurement noise (noise). When using an InSb detector, a cooling facility for keeping the temperature low is used. I need.

Also, in the conventional ESR device, the absorption energy that occurs when the unpaired electrons resonate is detected by a crystal diode detector, etc., and the minute signal is amplified and recorded, and an advanced device is required for amplification of the minute signal. there were.
In addition, in order to increase the strength of the magnetic field with a stationary static magnetic field in order to improve the measurement resolution, a large-scale facility such as a power supply and a cooling facility is required, and downsizing of the strong magnetic field ESR device is a problem.

  A high magnetic field / high frequency ESR measuring apparatus using a pulsed magnetic field to which magnetization detection by a cantilever according to the present invention is applied is made to solve the above problems.

  As a result of studying electron spin resonance (ESR) measurement for many years, the present inventors are able to perform highly sensitive ESR measurement with simpler equipment than before by combining a strong magnetic field generation by a pulse and a cantilever. In addition, by measuring the amount of magnetization reversal of the sample itself with a cantilever and detecting the magnetization reversal of the sample with the cantilever, the electron spin resonance itself can be directly observed with high sensitivity, thereby completing the present invention. It came.

  From the first aspect of the present invention, “cantilever, pulse magnetic field applying means for applying a pulse magnetic field to a sample attached to the cantilever, and electromagnetic wave application for irradiating the sample with a high frequency electromagnetic wave such as millimeter wave, submillimeter wave, terahertz, etc. And a cantilever-detecting electron spin resonance measuring apparatus characterized by detecting at least a bending displacement of the cantilever caused by a change in magnetic torque due to electron spin resonance of the sample. Is provided.

In the present invention, a sample is attached to the tip of a cantilever, a strong magnetic field is generated by a pulsed magnetic field, and a high frequency electromagnetic wave such as millimeter wave, submillimeter wave, terahertz, etc. is irradiated to generate magnetization caused by resonance of unpaired electrons in the sample. Thus, the deflection displacement due to the moment force acting on the cantilever is measured.
In other words, the spin level of electrons in a magnetic field is Zeeman split and the distribution of up and down spins is in an equilibrium state, but when an electromagnetic wave is irradiated here and the magnetic field is swept, the magnetic field energy and Zeeman splitting match. Absorption only occurs (ESR), and magnetization that deviates from the equilibrium state occurs at this time, and the change in magnetization is observed as the torque of the cantilever on which the sample is mounted.
It detects the physical displacement by electron spin resonance by detecting the deflection displacement of the cantilever using a micro displacement detection measurement such as an optical lever method or a piezo element resistance method. As a measurement method for detecting a small displacement acting on the cantilever, in addition to the optical lever method, a measurement by an optical fiber interferometer, a measurement by a focus error detection method, or a cantilever with a piezo element resistance can be used.

Since the ESR device according to the present invention does not use a cavity resonator, it can measure a wide range of millimeter waves, submillimeter waves, terahertz, and the like, and has a frequency-free measuring device, in particular, frequency-dependent measurement. This is a great merit for the measurement of minute sample systems.
For example, it can be applied to the determination of zero magnetic field splitting of hemoglobin.
Further, since the sensitivity of the cantilever is proportional to the absorption intensity, the higher frequency and the higher magnetic field measurement are more advantageous.

  In addition, in the conventional ESR apparatus, the method of observing the transmittance with an InSb detector cannot obtain sensitivity unless there is a certain amount of sample. In the case of a cantilever, even a high frequency / high magnetic field measurement is very small. Sensitivity is obtained with the sample.

Furthermore, the conventional ESR device creates a stationary static magnetic field with an electromagnet, the strength of the magnetic field is about 0.3 Tesla, and the transmitter that resonates unpaired electrons is a microwave transmitter that uses a frequency of about 10 GHz. On the other hand, the ESR measurement apparatus according to the present invention can sweep the magnetic field from about 0 Tesla to about 80 Tesla by using a pulsed magnetic field, and the frequency of electromagnetic waves can be from about 30 GHz to about 3000 GHz.
The record of the non-destructive pulse magnetic field is currently about 80 Tesla.
In the case of a stationary magnetic field, a large-scale facility is required to generate a magnetic field of 20 Tesla or higher, whereas in the case of the ESR device according to the present invention, a magnetic field of 20 Tesla or higher is reduced by using a pulsed magnetic field. Even large-scale facilities can be created.

  Electrons to which a magnetic field is applied undergo Zeeman splitting by spin, the energy level splits, and resonance absorption occurs when an electromagnetic wave having energy corresponding to this split level is incident. The stronger the applied magnetic field, the more stable the spin direction of irregular electrons that are difficult to observe. This is directly related to the sensitivity of ESR measurement. That is, in the present invention, a high magnetic field is generated even in a small-scale facility by a pulsed magnetic field, and the sensitivity of ESR measurement is improved.

  In addition, since the sample can be made minute by increasing the sensitivity, it is possible to increase the magnetic field uniformity even if a pulsed magnetic field is used, and to increase the resolution of the measurement in combination with the higher frequency.

  Next, according to the second aspect of the present invention, “a cantilever having a ferromagnetic material attached thereto, a sample, pulse magnetic field applying means for applying a pulse magnetic field to the sample, millimeter wave, submillimeter wave, terahertz, etc. At least an electromagnetic wave applying means for irradiating a high frequency electromagnetic wave and a detecting means for detecting the amount of bending of the cantilever, and detecting the bending displacement of the cantilever generated by the interaction between the ferromagnetic material and the sample due to electron spin resonance of the sample A cantilever-detecting electron spin resonance measuring apparatus ”is provided.

  Instead of attaching the sample to the cantilever as in the first aspect of the present invention, in the second aspect, by attaching a ferromagnetic material such as permalloy to the cantilever, the magnetization of the ferromagnetic material and the sample is allowed to interact. Thus, non-contact measurement of a sample is possible. By arranging the ferromagnet at the tip of the cantilever and the sample to face each other, a change in magnetization caused by electron spin resonance of the sample is regarded as a change in bending of the cantilever. Similarly to the first aspect, the second aspect uses a cantilever to capture the torque (deflection) change caused by the change in magnetization as an ESR signal, so that no cavity resonator is required and the electromagnetic wave frequency (magnetic field strength) to irradiate. Can be increased without limitation, thereby achieving higher sensitivity. According to the second aspect of the present invention, it is not necessary to attach the sample to the cantilever, the convenience is improved, and the measured sample can be easily collected.

  Next, according to a third aspect of the present invention, in the first aspect or the second aspect, the pulse magnetic field applying means is configured as a minicoil by miniaturizing the cantilever and the sample to narrow the magnetic field generation space. A cantilever-detecting electron spin resonance measuring apparatus including a small-capacitance capacitor is provided.

  Since the heart of an ESR measurement apparatus using a cantilever has a simple structure composed of a cantilever and a sample, a space that requires magnetic field generation can be easily reduced by miniaturizing the cantilever and the sample. In other words, a cantilever and a sample are installed inside the minicoil to form a minicoil pulse magnetic field. By using a mini-coil pulse magnetic field, the magnetic field space volume to which the magnetic field is squared corresponds to energy, so even if the same strong magnetic field is generated, a strong magnetic field can be generated with a very small capacitor in the mini-coil. It can be done. As a result, a table top cantilever detection ESR measurement device can be obtained.

  Currently, the inner diameter of a coil of a magnet (pulse magnet) that generates a pulsed magnetic field that is generally used is several tens of millimeters. For example, when a pulse magnet is used using a minicoil with an inner diameter of 3 mm or less, the magnetic field Since the energy of the capacitor for generating is proportional to the square of the magnetic field, the energy of the capacitor can be reduced from 100 kJ to several kJ.

  By using a mini-coil pulse magnet, the energy of the capacitor can be reduced, so that vibration due to the pulse magnet can be suppressed and the safety can be improved, and the device can be made compact by reducing the capacity of the capacitor.

  In addition, by miniaturizing the sample, it is possible to increase the magnetic field uniformity even when using a pulsed magnetic field, and it is possible to dramatically improve the resolution of measurement in combination with the increase in frequency.

  Since the ESR measurement apparatus according to the present invention performs magnetization detection by a cantilever method, it is suitable for measurement of a minute sample, has no temperature dependency, and does not require a cooling device like an IbSb detector. There is an effect that a simple detection circuit that only needs to be installed inside may be used.

  Moreover, since the ESR measurement apparatus according to the present invention uses a pulsed magnetic field, a high magnetic field of 20 Tesla or more can be generated in a small-scale facility, and the ESR measurement sensitivity can be increased. In addition, since measurement is performed using a pulsed magnetic field, the measurement is completed within a short time of several ms to several tens of ms, and so-called snapshot measurement is possible.

  Since the ESR measurement apparatus according to the present invention observes the change in magnetization due to electron spin resonance as the torque of the cantilever, the detection is possible regardless of the frequency, and there is a limit on the frequency by the detector as in the conventional ESR measurement. do not do. Further, the sensitivity of the cantilever is proportional to the absorption intensity, and the higher the frequency and the stronger the magnetic field, the more advantageous. Furthermore, because it can use wideband electromagnetic waves up to millimeter waves, submillimeter waves, and terahertz in a strong magnetic field by pulsed magnetic fields, it has a very high resolution, can distinguish similar free radicals, and can be applied to living bodies. It is.

  In addition, it can be applied to high-resolution nuclear magnetic resonance (NMR) by combining the frequency of electromagnetic waves of 1 GHz or more and a pulsed magnetic field.

  Hereinafter, an ESR measurement apparatus according to the present invention will be described in detail with reference to the drawings showing an embodiment of the present invention.

  An ESR measurement apparatus according to the present invention detects a cantilever, a pulse magnetic field applying means for applying a pulse magnetic field to a sample attached to the cantilever, an electromagnetic wave applying means for irradiating the sample with a high frequency electromagnetic wave, and a deflection amount of the cantilever And detecting the displacement of the bending amount of the cantilever generated by the change of the magnetic torque due to the electron spin resonance of the sample.

  FIG. 1 shows a configuration diagram of an embodiment of an ESR measurement apparatus according to the present invention. A sample 2 to be measured attached to the cantilever 4 is placed in a magnetic field generated by the electromagnet 1, and the sample 2 is irradiated with electromagnetic waves using an oscillator 3. The magnetic field is a high magnetic field generated by a pulse magnetic field application circuit 9 including a capacitor, a switch, and the like.

  The unpaired electrons in the sample have a magnetic moment, and when the unpaired electrons are in a strong magnetic field, resonance absorption that occurs when an electromagnetic wave is applied is electron spin resonance. There is a certain relationship between the strength of the magnetic field and the frequency of the electromagnetic wave, and the magnitude of electromagnetic wave absorption and the magnitude of the magnetic field at which absorption occurs depend on the number of unpaired electrons and the surrounding structure, respectively. Measurement and analysis of substances become possible.

  In the ESR measuring apparatus according to the present invention, the detecting means 5 for detecting the amount of bending of the cantilever detects the displacement of the amount of bending of the cantilever 4 caused by the change of the magnetic torque due to the electron spin resonance of the sample 2. As a method of detecting the amount of bending of the cantilever, as shown in FIG. 1, a strain gauge is built in the cantilever, and the displacement of the amount of bending of the cantilever is detected by measuring the voltage value that is the output of the strain gauge.

When measurement is performed using a pulsed magnetic field, the measurement is completed within a short time such as several tens of ms. Therefore, the measurement data of the output voltage value of the strain gauge is recorded using the digital memory 6, and the measured data is stored in the information processing terminal PC7. Is used to display and analyze measurement data.
In addition, in order to monitor the magnetic field by placing the coil in the magnetic field and measuring the induced electromotive force, the magnetic field measurement data is also recorded using the digital memory 6.

  FIG. 2 is a graph showing a change in the strength of the magnetic field with respect to time in the pulse magnetic field. The pulse magnetic field is a sinusoidal magnetic field change as shown in FIG. In order to cause electron spin resonance, a sample is irradiated with a certain electromagnetic wave from an oscillator. As described above, there is a certain relationship between the strength of the magnetic field and the frequency of the electromagnetic wave. Assuming that the intensity of the magnetic field that causes electron spin resonance at the frequency of the irradiated electromagnetic wave is Hm, as shown in FIG. 2, the condition for causing resonance is that the peak of the pulsed magnetic field exceeds the magnetic field of Hm. Therefore, the use of a pulsed magnetic field eliminates the need for magnetic field tuning for measurement.

  In addition, as shown in FIG. 2, when a pulsed magnetic field is used, the strength of the magnetic field causing electron spin resonance is Hm twice during a minute measurement time of the pulsed magnetic field, and the magnetic moment due to electron spin resonance of the sample is measured. The displacement of the bending of the cantilever generated by the change occurs twice.

  FIG. 3 shows the relationship between the strength of the magnetic field where electron spin resonance absorption occurs and the energy level of electrons. When unpaired electrons are placed in a magnetic field, the energy level is Zeeman split by the interaction between the magnetic field created by the spins of the unpaired electrons and the external magnetic field, and the electromagnetic wave to be radiated has energy hν (h: Planck's constant, (v: frequency of electromagnetic wave), electron spin resonance absorption occurs when an electromagnetic wave equal to the energy difference between adjacent levels is applied. The spin of unpaired electrons is the same as that of a small magnet, and it is considered that the electron spin resonance absorption causes a transition to a higher energy level and the direction of the spin is reversed. This also reverses the direction of the small magnet. Accordingly, the magnetism of the sample attached to the cantilever changes due to electron spin resonance absorption, which causes a change in the magnetic moment acting on the cantilever, resulting in displacement of the deflection amount of the cantilever.

Next, a result of actually measuring using Co (NH ₄ ) ₂ (SO ₄ ) ₂ .6H ₂ O having transition metal ion Co ²⁺ as a sample using the ESR measuring apparatus according to the present invention will be shown. FIG. 4 shows the time dependence of the pulse magnetic field strength actually used. FIG. 4 shows that a pulse width is about 60 ms and a sinusoidal magnetic field having a peak magnetic field strength of about 2 Tesla is generated.

Here, the magnetic ion Co ²⁺ of Co (NH ₄ ) ₂ (SO ₄ ) ₂ .6H ₂ O used in this measurement has a single crystal size of 100 × 100 × 100 μm ³ and a mass of about 0.8 μg. This corresponds to about 10 ¹⁵ electron spins.

FIG. 5 is a graph showing the time dependence of magnetic torque acting on a cantilever when a Co (NH ₄ ) ₂ (SO ₄ ) ₂ · 6H ₂ O sample is attached to a cantilever with a built-in strain gauge. . In FIG. 5, “on” is a measurement when the electromagnetic wave is irradiated, and “off” is a measurement result when the electromagnetic wave is not irradiated. Here, the frequency of the irradiated electromagnetic wave is 80 GHz, and the measurement temperature is 1.7K.

  The cantilever is a micro cantilever (400 μm × 50 μm × 4 μm, spring constant k = 2 N / m, resonance frequency f = 35 kHz) manufactured by Seiko Epson, Inc. Using.

  In FIG. 5, in the measurement result performed while irradiating the electromagnetic wave at “on”, in addition to the normally observed magnetic torque, the displacement of the hump-shaped magnetic torque is observed at two locations indicated by arrows in the figure. You can see that This is because, as described above, when a pulse magnetic field is used, the strength of the magnetic field causing electron spin resonance is Hm twice during the generation time of the pulse magnetic field, and is generated by a change in magnetic moment due to electron spin resonance of the sample. This corresponds to the fact that the displacement of the bending of the cantilever occurs twice.

  Although there is a slight deviation in the deflection displacement that occurs twice due to the problem of the magnetic field base, almost the same value is shown, and the reliability of the data is enhanced. The first data is adopted as measurement data.

  Here, in this measurement, a strain gauge is used as a detection means for detecting the amount of bending of the cantilever, but an optical lever or the like may be used to further increase the sensitivity. The sensitivity on the vertical axis in FIG. 5 is increased, and more accurate measurement can be performed.

FIG. 6 shows the magnetic field dependence of the magnetic torque in the Co (NH ₄ ) ₂ (SO ₄ ) ₂ .6H ₂ O sample. As in FIG. 5, “on” in the figure is a measurement when the electromagnetic wave is irradiated, and “off” is a measurement result when the electromagnetic wave is not irradiated. Here, the frequency of the irradiated electromagnetic wave is 80 GHz, and the measurement temperature is 1.7K.
It can be seen that when the strength of the magnetic field is around 1.6 Tesla, the displacement of the bending of the cantilever caused by the change of the magnetic moment due to the electron spin resonance of the sample occurs.

FIG. 7 shows the data obtained by subtracting the magnetic torque of the Co (NH ₄ ) ₂ (SO ₄ ) ₂ · 6H ₂ O sample when the electromagnetic wave is not irradiated from the magnetic torque when the electromagnetic wave is irradiated as the background. Yes. The part indicated by the arrow in the figure corresponds to the displacement of the magnetic torque observed when the electromagnetic wave is irradiated. As can be seen from the figure, with the frequency of electromagnetic waves to be irradiated, such as 50 Hz, 80 Hz, and 130 Hz, a signal in which the displacement of the magnetic torque is observed is shifted to a high magnetic field. This means that the observed signal suggests the possibility of electron spin resonance.

FIG. 8 is a plot of the frequency of the irradiated electromagnetic wave and the strength of the resonance magnetic field in a Co (NH ₄ ) ₂ (SO ₄ ) ₂ .6H ₂ O sample. The obtained data point is located almost on a straight line passing through the origin, and g = 3.55 of electron spin resonance was obtained from this linear equation. This g value is a reasonable value as the g value of Co ²⁺ ions.

Next, using the ESR measurement apparatus according to the present invention, Mn (NH ₄ ) ₂ (SO ₄ ) ₂ .6H having manganese ions Mn ²⁺ , which is one of transition metal ions, which is a sample different from Example 1. _The results of measurement using ₂ O as a sample are shown.

FIG. 9 shows data obtained by subtracting the magnetic torque of the Mn (NH ₄ ) ₂ (SO ₄ ) ₂ · 6H ₂ O sample when the electromagnetic wave is not irradiated from the magnetic torque when the electromagnetic wave is irradiated as a background. Yes. The part indicated by the arrow in the figure corresponds to the displacement of the magnetic torque observed when the electromagnetic wave is irradiated. As can be seen from the figure, the signal at which the displacement of the magnetic torque is observed is shifted to a high magnetic field in accordance with the frequency of the electromagnetic wave to be irradiated, such as 50 Hz and 80 Hz.

FIG. 10 is a plot of the frequency of the irradiated electromagnetic wave and the strength of the resonant magnetic field in a sample of Mn (NH ₄ ) ₂ (SO ₄ ) ₂ .6H ₂ O. The obtained data points are located almost on a straight line passing through the origin, and g = 2.14 of electron spin resonance was obtained from this linear equation. This g value is a reasonable value as the g value of Mn ²⁺ ions.

In FIG. 11, the block diagram in the Example of the ESR measuring apparatus (non-contact type | mold measurement) which concerns on the 2nd viewpoint of this invention is shown. Unlike the configuration of Example 1 in FIG. 1, the sample is not attached to the cantilever, but a ferromagnetic material 10 such as permalloy is attached to the tip of the cantilever 4. And it arrange | positions so that the ferromagnetic 10 and the sample 2 of the front-end | tip part of the cantilever 4 may be made to oppose. Magnetization caused by electron spin resonance of the sample 2 is caused to interact using the ferromagnetic material 10 and is regarded as a change in the bending of the cantilever 4 to enable non-contact measurement of the sample 2.
In FIG. 11, the detecting means 5 for detecting the bending amount of the cantilever and the pulse magnetic field applying circuit 9 in FIG. 1 are not shown.

  The ESR measurement apparatus according to the present invention can be widely used in the fields of chemistry, biology, medicine, etc. as one of chemical sample analysis apparatuses, and in particular, has higher resolution than conventional ESR apparatuses due to high frequency and high magnetic field. Is high, can distinguish similar free radicals, and is highly applicable to living bodies.

The block diagram in the Example of the ESR measuring apparatus which concerns on this invention is shown. The graph which shows the time of a pulse magnetic field and the change of a magnetic field is shown. The relationship between the strength of the magnetic field where electron spin resonance absorption occurs and the energy level of electrons is shown. The time dependence of the pulse magnetic field intensity actually used is shown. The time dependence of the magnetic torque in the Co (NH ₄ ) ₂ (SO ₄ ) ₂ · 6H ₂ O sample is shown. The magnetic field dependence of the magnetic torque in the Co (NH ₄ ) ₂ (SO ₄ ) ₂ · 6H ₂ O sample is shown. Co magnetic torque when the _{(NH 4) 2 (SO 4} ) without applying an electromagnetic wave in a sample of ₂ · 6H ₂ O, is a graph showing the data obtained by subtracting the background from the magnetic torque when irradiated with electromagnetic waves. The graph figure of what plotted the frequency of the electromagnetic wave irradiated and the intensity of the resonant magnetic field in the sample of Co (NH ₄ ) ₂ (SO ₄ ) ₂ · 6H ₂ O is shown. Mn magnetic torque when the _{(NH 4) 2 (SO 4} ) without applying an electromagnetic wave in a sample of ₂ · 6H ₂ O, is a graph showing the data obtained by subtracting the background from the magnetic torque when irradiated with electromagnetic waves. _{Mn (NH 4) 2 (SO} 4) Although plotting the intensity of the frequency and the resonance magnetic field of the electromagnetic wave irradiated in a sample of ₂ · 6H ₂ O shows a graph. The block diagram in the Example of the ESR measuring apparatus (non-contact type measurement) which concerns on the 2nd viewpoint of this invention is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electromagnet 2 Sample 3 Oscillator 4 Cantilever 5 Detection means which detects bending amount of cantilever 6 Digital memory 7 Information processing terminal PC
8 Irradiated electromagnetic wave 9 Pulsed magnetic field application circuit 10 Ferromagnetic material

Claims (4)

  A cantilever, pulsed magnetic field applying means for applying a pulsed magnetic field to a sample attached to the cantilever, electromagnetic wave applying means for irradiating the sample with a high frequency electromagnetic wave such as millimeter wave, submillimeter wave, terahertz, and the amount of bending of the cantilever A cantilever-detecting electron spin resonance measuring apparatus comprising: at least a detecting unit; and detecting a bending displacement of the cantilever generated by a change in magnetic torque due to electron spin resonance of the sample.   A cantilever with a ferromagnetic material, a sample, a pulsed magnetic field applying means for applying a pulsed magnetic field to the sample, an electromagnetic wave applying means for irradiating the sample with a high frequency electromagnetic wave such as millimeter wave, submillimeter wave, terahertz, and the bending of the cantilever A cantilever-detecting electron spin resonance measuring apparatus, comprising: a detecting means for detecting a quantity; and detecting bending displacement of the cantilever caused by the interaction between the ferromagnetic material and the sample due to electron spin resonance of the sample.   3. The cantilever according to claim 1 or 2, wherein the pulse magnetic field applying means is constituted by a mini-coil and a small-capacitance capacitor by miniaturizing the cantilever and the sample to narrow a magnetic field generation space. Detection electron spin resonance measuring device. 4. The cantilever detection electron spin resonance measuring apparatus according to claim 1, wherein the method of detecting the bending displacement of the cantilever is a micro displacement detection measurement such as an optical lever method or a piezo element resistance method.

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