JPS61162763A - Susceptibility measuring apparatus - Google Patents

Abstract

PURPOSE:To enable measurement of susceptibility of a sample simply and accurately, by applying a secondary grade magnetic field to a sample to be measured arranged in a magnetostatic field to detect the cycle of vibration of the sample in the magnetic field. CONSTITUTION:Current is fed to coils 3 and 4 from a secondary grade magnetic field control means 10 to generate a secondary grade magnetic field with a parabolic intensity distribution overlapping an electrostatic field generated with electromagnetic generation coils 1 and 2. When an external force is applied to a sample 5 hung at the central part of the secondary grade magnetic field with a slender string, the sample 5 vibrates. Under such a condition, the sample 5 is irradiated with light from a light emitter 6 and the light partly intercepted by the sample 5 is detected with a photodetector 7. The output of the photodetector 7 is fed to a cycle measuring device 8 to measure the cycle thereof and the results of the measurement are fed to a computer 9 to compute and display the susceptibility.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a magnetic susceptibility measuring device that can easily measure the magnetic susceptibility of a sample with high precision. When a first-order gradient magnetic field is applied to the sample, a static force is applied to the sample.

Since this static force corresponds to the magnetic susceptibility of the sample, this force is measured with a balance to determine the magnetic susceptibility of the sample. That is, the magnetic susceptibility of the sample is χ.

If the magnetic susceptibility of the medium is χ', the strength of the static magnetic field is Hoe, and the sample volume is V, then the force FZ applied to the sample is:
H Fz −V (χ−χ′)H revision ・・・・・・■. Here, H−H@+a, z %, a.

, and the formula is as follows.

1”z −v (z z#) Ho at...
.=■ Therefore, if tJFz is measured, the magnetic susceptibility χ of the sample can be found based on this equation 0.

[Problems to be solved by the invention] However, since the above-mentioned forces F and Z are static forces, the detection signal becomes a direct current, and noise signals caused by drift etc. are superimposed, so they cannot be accurately detected. Unable to measure magnetic susceptibility.

The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a magnetic susceptibility measuring device that can easily measure the magnetic susceptibility of a sample with high accuracy.

[Means for solving the same illumination point] The first magnetic susceptibility measuring device based on the present invention includes a static magnetic field generating means and a means for applying a secondary gradient magnetic field to a sample to be measured placed in the static magnetic field. It is characterized by comprising a secondary gradient magnetic field generating means, a means for detecting the period of vibration of the sample in the magnetic field, and a means for calculating the magnetic susceptibility of the sample from the vibration period of the sample.

Further, a second magnetic susceptibility measuring device based on the present invention is a second magnetic susceptibility measuring device based on the first
The magnetic susceptibility measuring device is characterized by comprising a primary gradient magnetic field generating means for applying a primary gradient magnetic field to the sample, and a means for periodically changing the intensity of the primary gradient magnetic field.

[Operation] In the first apparatus based on the present invention, the sample to be measured is placed in a magnetic field in which a secondary gradient magnetic field is superimposed on a static magnetic field.

Here, if at is the gradient of the secondary gradient magnetic field, the magnetic field H in which the sample is placed is expressed as follows.

H=Ho +az Z2 Therefore, the force Fz applied to the sample is 1"z -2v (Z-Z')Ho a2Z...
...■ becomes. Here, if the mass of the sample is -m, then the equation of motion is derived. However, ω2-2az Ho V (Z' -Z)/m...
...■. Since this 0th equation expresses a simple harmonic motion of the angular frequency ω, the magnetic susceptibility χ of the sample can be determined from the 0th equation by measuring the frequency (period) of the vibration of the sample.

In the second apparatus based on the present invention, the sample to be measured is placed in a magnetic field in which a secondary gradient magnetic field and a primary gradient magnetic field are superimposed on a static magnetic field. Here, al is the gradient of the primary gradient magnetic field,
When at is the gradient of the secondary gradient magnetic field, the magnetic field H in which the sample is placed is expressed as follows.

H=Hol-at Z+az Z2 Therefore, the force FZ applied to the sample is: Fz -V (χ-χ')
2az z) ・・・・・・■. Here, if the mass of the sample is m, then the equation of motion is derived. The above equation can be expressed as follows within the range where terms of second order or higher order can be ignored.

+ (as ” +2'az Ho)
Z ]. Here, ωo 2-2az Ho V (Z' -z)/m...
...■ f-V (χ-χ',) as Ha. However, 2 a2Ho, > at 2 . Note that the above equation 0 represents the motion of the simple pendulum when external force f is applied.

Here, the strength of the primary gradient magnetic field is controlled so that the force applied to the sample by the primary gradient magnetic field and gravity are balanced. Furthermore, the strength of this primary gradient magnetic field is varied sinusoidally at an angular frequency close to ω0 in the above equation 0. As a result, the sample is in a resonant state and the first device according to the invention In comparison, the sample vibrates relatively large and continuously, making it easy to measure the frequency (period).

[Example 1 An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

In Figure 1, 1.2 is a static magnetic field generating coil, 3.4
is a coil for generating a secondary gradient magnetic field. The coil 1.2.
By passing an appropriate current through 3.4, a static magnetic field and a secondary gradient magnetic field are generated, and the sample to be measured 5 is placed in a space where these two magnetic fields are superimposed. Reference numeral 6 denotes a light emitter for irradiating light onto the sample, and the light from the light emitter 6 is received by a light receiver 7. The signal detected by the light receiver 7 is supplied to a period measuring device 8 to determine the period of the signal,
A signal corresponding to the period is supplied to the computer 9.

The computer 9 includes the secondary gradient magnetic field generation coil 3.4.
The secondary gradient magnetic field control means controls the current supplied to the magnetic field.

In the configuration as described above, the static magnetic field generating coil 1.2
A desired static magnetic field is generated by supplying an appropriate current to the magnet. Furthermore, a current is supplied from the secondary gradient magnetic field control means 10 to the coil 3.4, and a secondary gradient magnetic field having, for example, a parabolic intensity distribution is generated, superimposed on the static magnetic field. The sample 5 is placed in the center of this secondary gradient magnetic field, suspended by a thin thread, but if an external force is applied to the sample 5 in this state, for example, by pushing the sample with a desired force, The sample 5 vibrates. Since the sample 5 is subjected to the force 1''z shown in the 0th equation due to the superimposed magnetic field, the sample vibrates at the angular frequency ω shown in the 0th equation. , light is emitted from a light emitter 6, and the light partially blocked by the sample is detected by a light receiver 7.The amount of light incident on the light receiver 7 depends on the vibration of the sample 5. Therefore, the output signal of the light receiver 7 becomes a signal that changes in a sinusoidal manner with a period ω.The sine wave signal is supplied to a period measuring device 8 and its period is measured. The result is supplied to the computer 9. The computer 9 calculates the magnetic susceptibility χ of the sample 5 based on the 0th equation from the supplied periodic signal, and records the value with a recorder (not shown).
Display by.

In the apparatus shown in FIG. 1 described above, when an external force is applied to the sample, the sample starts to vibrate, but this vibration is a damped vibration and gradually weakens. The embodiment shown in FIG. 2 improves this point and makes the sample vibrate continuously and greatly.

In FIG. 2, the same components as those in FIG. 1 are given the same numbers, and detailed explanation thereof will be omitted. In this embodiment, a static magnetic field generating coil 1.2 and a secondary gradient magnetic field generating coil 3 are used.
．． 4, primary gradient magnetic field generating coils 11 and 12 controlled by the primary gradient magnetic field control means 10 are arranged. In this example, the sample 5 is placed in a space where a primary gradient magnetic field and a secondary gradient magnetic field are superimposed on a static magnetic field.
Next, if the force applied to the sample 5 by the gradient magnetic field is equal to the gravity that the sample receives, then if it is equal to the gravity that would be received by suspending the sample with a string, etc., then the sample can be placed in the center of the superimposed magnetic field without being suspended with a string, etc. I can do it. In this state, if the primary gradient magnetic field control means 11 is controlled by a command from the computer 9 and the current supplied to the primary gradient magnetic field generating coils 12 and 13 is varied in a sinusoidal manner, this variation in magnetic field strength is When the angular frequency is equal to ω0 shown in the zeroth equation, the sample enters a resonant state and vibrates greatly.

On the other hand, if the variation in magnetic field strength is different from ω0, the variation in the sample will be slight. Here, the period of fluctuation of the primary gradient magnetic field is continuously swept, and the state of fluctuation of the sample 5 during that period is monitored by the optical receiver 7.
If the amount of light incident on the photoreceptor 7 is monitored, it can be seen that when the vibration of the sample reaches a resonance state, the amount of light incident on the photodetector 7 fluctuates extremely. The computer 9 recognizes the cycle when this sample fluctuates greatly, and fixes the cycle of the excitation current supplied from the primary gradient magnetic field generating means 11 to the coils 12, 13 to this revealed cycle. As a result, the sample 5 is always in a resonant state and continuously fluctuates greatly, so that it can be cycled.

Note that the present invention is not limited to the embodiments described above, and many modifications are possible. For example, although light was used to measure the period of vibration of the sample, a device that mechanically measures vibrations may also be used. Further, as the magnetic field generating means, it is possible to use not only an air-core coil but also other magnet devices.

[Effect] As detailed above, in the present invention, since the sample is placed in a magnetic field in which a static magnetic field and a secondary gradient magnetic field are superimposed, it is possible to apply vibrations to the sample according to the magnetic susceptibility. By measuring the period of this vibration, the magnetic susceptibility can be determined. Since this vibration is detected as an AC signal, it is possible to accurately measure the period of vibration corresponding to the magnetic susceptibility without being affected by DC noise components such as sample drift. In addition, in the second magnetic susceptibility measuring device based on the present invention, the sample is placed in a magnetic field in which a static magnetic field, a secondary gradient magnetic field, and a primary gradient magnetic field are superimposed, so that the sample is placed in a large continuous field. This allows for more accurate measurements.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are diagrams each showing an embodiment of the present invention. 1.2... Coil for static magnetic field generation 3.4... Coil for secondary gradient generation 5... Sample to be measured 6... Light generator 7...
Receiver 8...Period measuring device 9...Computer

Claims (2)

[Claims] (1) A static magnetic field generating means, a secondary gradient magnetic field generating means for applying a secondary gradient magnetic field to a sample to be measured placed in the static magnetic field, and detecting the period of vibration of the sample in the magnetic field. A magnetic susceptibility measuring device comprising means for calculating the magnetic susceptibility of a sample from a vibration period of the sample. (2) A static magnetic field generating means, a secondary gradient magnetic field generating means for applying a secondary gradient magnetic field to a sample to be measured placed in the static magnetic field, and a primary gradient magnetic field generating means for applying a primary gradient magnetic field to the sample. a gradient magnetic field generating means, a means for periodically changing the intensity of the primary gradient magnetic field, a means for detecting the period of vibration of the sample in the magnetic field, and calculating the magnetic susceptibility of the sample from the vibration period of the sample. A magnetic susceptibility measuring device comprising means for measuring magnetic susceptibility.