JP3769610B2 - Electric resistance in magnetic field, Hall effect measuring device using MPMS magnetization measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for measuring electric resistance and Hall effect in a magnetic field for measuring the electric resistance and Hall effect of various materials in a magnetic field, or both, and in particular, measurement of magnetization of MPMS that has been widely used conventionally. By using the apparatus, it is not necessary to use a special liquid helium experimental apparatus, and the magnetic field using the MPMS magnetization measuring apparatus that can measure the electric resistance and the Hall effect in the magnetic field of various materials by simple means. The present invention relates to a medium electrical resistance and Hall effect measuring device.
[0002]
[Prior art]
Conventionally, measurement of electric resistance and Hall effect in a magnetic field at a low temperature of about 2K or less at room temperature is performed by inserting a thin liquid helium dewar into the gap of a large electromagnet or using a large dewar incorporating a superconducting magnet. I came.
[0003]
[Problems to be solved by the invention]
In the conventional apparatus as described above, a system using an electromagnet must be very heavy and large, and since heat generation is large, it is not preferable in terms of energy utilization efficiency. In addition, thin dewars are poor in liquid helium, cannot be used for long periods of time, and require skill in operation.
[0004]
In a system using a superconducting magnet, there are almost no problems related to the electromagnet. However, in order to cool a superconducting magnet having a large heat capacity to 4.2 K, a large amount of liquid helium is required. Therefore, it is a waste of liquid helium and time to cool the room temperature superconducting magnet to 4.2 K each time an experiment is performed.
[0005]
On the other hand, a large number of laboratories of solid physical properties have a magnetization measuring device called MPMS (Magnetic Property Measurement System) (hereinafter abbreviated as “MPMS magnetization measuring device”) manufactured by Quantum Design, USA. The device is basically always filled with liquid helium. Therefore, if this MPMS magnetization measuring apparatus can be used for measurement of electric resistance and Hall effect in a magnetic field, measurement can be easily performed at any time and research efficiency is increased, and liquid helium is not wasted.
[0006]
Therefore, the present invention is commercially available and widely used on the basis of the above idea, and can easily measure the electric resistance and Hall effect in a magnetic field by using a magnetization measuring device always filled with liquid helium. The main object is to provide a resistance and Hall effect measuring device.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention according to claim 1 of the present application uses a liquid-helium cooling means, a superconducting magnet, a magnetic field forming means, a temperature adjusting means, and a SQUID element having a magnetic field adjusting means as a detector. A measuring device is used, and includes a rod that can be inserted into a magnetization measuring device that fixes the sample and uses the SQUID element as a detector, and a measuring unit that measures the electrical resistance or Hall voltage of the sample . Electrical resistance in a magnetic field using a magnetization measuring device using a SQUID element as a detector, comprising a switching means capable of arbitrarily switching a plurality of rod samples, temperature sensors, and measuring Hall elements , and Hall Effect measuring device.
[0009]
According to a second aspect of the present invention, the measuring means includes an electrical resistance measurement program or a Hall effect measurement program, and operates the program in association with the operation of the temperature adjusting means and the magnetic field adjusting means. The electrical resistance or the Hall effect is automatically measured , and the electrical resistance in the magnetic field and Hall effect measuring apparatus using the magnetization measuring apparatus using the SQUID element as a detector according to claim 1 is provided.
[0010]
According to a third aspect of the present invention, the measuring means includes means for measuring an electric resistance corresponding to a temperature change by adjusting the temperature adjusting means and an electric resistance corresponding to a magnetic field change by adjusting the magnetic field adjusting means. A magnetic field electric resistance and Hall effect measuring device using a magnetization measuring device using the SQUID element according to claim 1 as a detector .
[0011]
The invention according to claim 4 is characterized in that the measuring means includes a digital voltmeter and a constant current power source , and a magnetic field using a magnetization measuring device using a SQUID element as a detector according to claim 1. This is a medium electrical resistance and Hall effect measuring device.
[0012]
According to a fifth aspect of the present invention, the measuring means includes an AC resistance bridge. The electric resistance in a magnetic field using the magnetization measuring apparatus using the SQUID element as a detector according to the first aspect, This is a Hall effect measuring device.
[0013]
In the invention according to claim 6 , in the magnetization measuring apparatus using the SQUID element as a detector , a shunt resistor is connected in series between the output terminal of the superconducting magnet excitation power source and the superconducting magnet, 2. A device for measuring electric resistance and Hall effect in a magnetic field using a magnetization measuring device using a SQUID element as a detector according to claim 1, further comprising means for reading a magnetic field from a potential difference of a shunt resistor connecting portion. is there.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
In view of the above-mentioned problems of the prior art, the present invention is commercially available and widely used, and an MPMS magnetization measuring apparatus is used as a magnetization measuring apparatus that is always filled with liquid helium, and the electric resistance in the magnetic field and / or the Hall effect are both. Developed a device to measure. In this device, no modification is required on the side of the MPMS magnetization measuring device, and a rod for measuring electric resistance and Hall voltage is inserted in place of the rod for measuring magnetization used in the MPMS magnetization measuring device, It can be implemented simply by adding members and using a control program.
[0015]
The embodiment of the present invention will be described more specifically. In the magnetic field resistance and Hall effect measuring apparatus shown in FIG. 1, a magnetization measuring apparatus that has been widely used as an MPMS magnetization measuring apparatus as described above. In this apparatus, a rod mounted with a sample can be taken in and out of the liquid helium container 2 inside through the opening 3.
[0016]
The magnetization measuring apparatus 1 can detect a micro magnetic field generated by a magnetic sample fixed to a rod inserted from the opening 3 with a SQUID element that applies the Josephson effect of a superconductor. Thus, it is possible to measure the magnetic susceptibility, the magnetization curve, and the Meissner effect of a superconductor sample.
[0017]
The magnetization measuring device 1 includes a magnetization measuring device control device 4 using a personal computer for mainly inputting and processing a measurement value of a micro magnetic field of a sample inserted in the container 2. Further, in the magnetization measuring device control device 4, in order to set a predetermined condition in the measurement, measurement data is taken in at least from the magnetic measuring unit 8, the temperature measuring unit 10, etc. provided in the magnetization measuring device 1, and the magnetic adjusting unit. 9, a predetermined magnetic field state is maintained, and the temperature adjusting unit 11 can maintain a predetermined temperature state. In the magnetic measurement unit 8, the magnetic field can be calculated by multiplying the current flowing through the superconducting magnet by a predetermined coefficient.
[0018]
Such a conventionally used magnetization measuring device 1 is used, and in the present invention, a rod 5 for measuring electric resistance and Hall voltage in a magnetic field is used as a rod inserted from the opening of the magnetization measuring device 1, and this rod 5 A sample is attached to and inserted into the container 2. The rod 5 has a sample stage that can apply a magnetic field vertically to a flat sample. A connector 6 of the rod 5 is connected to a switch system 12 that performs an operation described later by a dedicated cable 13. In the figure, only one channel of 4-wire measurement is shown, but in actuality, one having more channels is used.
[0019]
A digital voltmeter 14 and a low current power source 15 are connected to the switch system 12 and can be controlled by an electric resistance / hall voltage measurement control device 16. The electrical resistance / hall voltage measurement control device 16 can select a plurality of samples mounted on the rod 5 by the switch system 12, and can switch between a plurality of temperature sensors provided at various locations on the rod 5 to capture measurement data. Further, the magnetic field measuring Hall element fixed to the rod 5 can be selected. Such switching and selection can be automatically measured by program software recorded in the electrical resistance / hall voltage measurement control device 16.
[0020]
Using the apparatus as described above, in the present invention, the temperature change of the electric resistance is measured while fixing the magnetic field, the change of the electric resistance due to the magnetic field is measured while keeping the temperature constant, and the Hall effect is measured. Various other measurements can be performed. Hereinafter, these will be described based on the operation flow of FIGS.
[0021]
In order to measure the temperature change of the electric resistance while fixing the magnetic field using the above apparatus, for example, the measurement can be performed along the operation flow shown in FIG. In other words, when measuring the change in electrical resistance with temperature while the magnetic field is fixed at a predetermined value, the magnetic field is first set to the required value by the computer on the MPMS magnetization measuring device side that is usually used for controlling the magnetization measurement. Further, a desired temperature change is programmed (step S1).
[0022]
Next, the electrical resistance / Hall voltage measurement control device 16 shown in FIG. 1 as a computer on the apparatus side starts an electrical resistance measurement program, inputs measurement conditions and the like, and starts measurement (step S2). Thereafter, the temperature program of the magnetization measuring device control device 4 shown in FIG. 1 as a computer on the MPMS magnetization measuring device side is started (step S3). Next, the electrical resistance at each temperature is measured while measuring the temperature with the computer on the apparatus side (step S4). By continuing such measurement of electrical resistance, it is possible to measure electrical resistance characteristics corresponding to temperature changes (step S5). In this way, this apparatus monitors the temperature independently, and can automatically acquire data by detecting a temperature change in the sample space.
[0023]
Next, in the process of measuring the change due to the magnetic field of the electrical resistance while keeping the temperature at a predetermined value, for example, as shown in FIG. 3, the temperature is first set by a computer on the MPMS magnetization measuring apparatus side, and the desired magnetic field change is performed. Is programmed (step S11). Next, the electrical resistance measurement program is started by the computer on the apparatus side, and the temperature is input to start measurement (step S12). Thereafter, the magnetic field program of the computer on the MPMS magnetization measuring apparatus side is started (step S13). Next, the electrical resistance in each magnetic field is measured by the computer on the apparatus side (step S14), and the electrical resistance characteristic corresponding to the magnetic field change is measured (step S15). In this way, the present apparatus independently monitors the magnetic field, and can automatically output data by detecting a magnetic field change in the sample space.
[0024]
Next, in the Hall effect determination process, for example, as shown in FIG. 4, a program for changing the magnetic field is first set after the temperature is kept constant at a specific value on the computer on the MPMS magnetization measuring apparatus side (step S21). ). Is manner of change of the magnetic field at this time is, for example, when the maximum magnetic field and _{H 0} is used in the _measurement, -H _0, -0.9H _0, starting from -H ₀ as -0.8H ₀ 0.1H through the 0T continue to increase at ₀ increments until + H ₀ so as to increase.
[0025]
Next, it is determined whether or not the creation of the magnetic field change program for each temperature in the desired temperature range has been completed (step S22). If it is determined that the creation of the program has not been completed, another temperature is further determined. The magnetic field change program is assembled (step S30), the process returns to the original step S22 again, and the above operation is repeated.
[0026]
When it is determined in step S22 that the creation of the magnetic field change program for each temperature in the desired temperature range has been completed, the Hall effect measurement program is started on the computer on the apparatus side, and the measurement conditions are input to perform measurement. Is started (step S23). Thereafter, the program is started on the computer on the MPMS magnetization measuring apparatus side (step S24). Next, the signal from the Hall voltage terminal of the sample is measured on the computer side of the apparatus, and the value is fitted with a straight line as a function of the magnetic field (step S25).
[0027]
Next, it is determined whether or not the measured value can be fitted with a straight line (step S26). When it is determined that the measured value can be fitted with a straight line, the process proceeds to step S31, and the Hall coefficient is obtained from the slope of the straight line. When it is determined in step S26 that the measured value cannot be fitted with a straight line, an operation of taking the difference of the Hall voltage when the magnetic field is + H and -H and dividing by 2 is performed (step S27).
[0028]
Next, it is determined whether or not the value obtained by performing such an operation can be fitted with a straight line (step S28). When this can be fitted with a straight line, the process proceeds to step S31, and the Hall coefficient is obtained from the inclination of the straight line as described above. . If it is determined that the straight line cannot be fitted, it is determined that the sample exhibits an abnormal Hall effect (step S29). In this way, the temperature change of the Hall coefficient can be measured.
[0029]
The standard measurement system using the direct current method has been described above. However, as a modification, a system using an AC resistance bridge instead of the combination of the digital voltmeter 14 and the constant current power supply 15 may be used. In that case, the latter can generally obtain a better S / N ratio. However, although the cost is high, many of the above-mentioned drawbacks of the conventional measuring apparatus can be solved.
[0030]
Also, the Hall element on the sample holder can be omitted in order to further reduce the cost compared to the standard system. In this case, a shunt resistor is inserted in series between the output terminal of the superconducting magnet excitation power source on the MPMS magnetization measuring device side and the superconducting magnet, and the magnetic field is read from the voltage generated there. In this case, the user needs to input the initial value of the magnetic field to the measurement program on the apparatus side. Further, if a shunt resistor is connected to the MPMS magnetization measuring device side, the work must be performed, which requires more work than the above-described one that does not require any modification on the MPMS magnetization measuring device side.
【The invention's effect】
Since the present invention is configured as described above, it is commercially available and widely used, and by using an MPMS magnetization measuring apparatus that is always filled with liquid helium, the electric resistance and Hall effect in a magnetic field can be easily and inexpensively obtained. Can be measured.
[Brief description of the drawings]
FIG. 1 is a system outline diagram showing the overall system configuration of an embodiment of the present invention.
FIG. 2 is an operation flow chart when performing a measurement process of a change in electric resistance with temperature under a fixed magnetic field using the apparatus of the present invention.
FIG. 3 is an operation flow diagram when performing a measurement process of a change in electrical resistance with temperature under a constant temperature using the apparatus of the present invention.
FIG. 4 is an operation flow diagram when performing Hall effect determination processing using the apparatus of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 MPMS magnetization measuring device 2 Container 3 Opening 4 Magnetization measuring device control device 5 Rod 6 Connector 8 Magnetic measurement unit 9 Magnetic adjustment unit 10 Temperature measurement unit 11 Temperature adjustment unit 12 Switch system 13 Measurement cable 14 Digital voltmeter 15 Constant current Power supply 16 Electric resistance / Hall voltage measurement control device

Claims (6)

Using a magnetization measuring device using a SQUID element as a detector, equipped with a cooling means using liquid helium, a superconducting magnet, a magnetic field forming means, a temperature adjusting means, and a magnetic field adjusting means
A rod that can be inserted into a magnetization measuring apparatus that fixes a sample and uses the SQUID element as a detector ;
Measuring means for measuring the electrical resistance or Hall voltage of the sample,
As the measuring means, a magnetization measuring apparatus using a SQUID element as a detector, comprising switch means capable of measuring by arbitrarily switching a plurality of rod samples, temperature sensors, and measuring Hall elements, was used. Electric resistance in a magnetic field, Hall effect measuring device. The measuring means includes a program for measuring electric resistance or a program for measuring Hall effect, and operates the program in association with the operation of the temperature adjusting means and the magnetic field adjusting means to automatically set the electric resistance or Hall effect. An apparatus for measuring electric resistance and Hall effect in a magnetic field using a magnetization measuring apparatus using the SQUID element according to claim 1 as a detector . 2. The measuring means includes means for measuring an electric resistance corresponding to a temperature change by adjusting the temperature adjusting means and an electric resistance corresponding to a magnetic field change by adjusting the magnetic field adjusting means. A magnetic field electric resistance and Hall effect measuring apparatus using a magnetization measuring apparatus using the described SQUID element as a detector . 2. The apparatus for measuring electric resistance and Hall effect in a magnetic field using a magnetization measuring apparatus using a SQUID element as a detector according to claim 1, wherein said measuring means comprises a digital voltmeter and a constant current power source. 2. An apparatus for measuring electric resistance in a magnetic field and Hall effect using a magnetization measuring apparatus using a SQUID element as a detector according to claim 1, wherein said measuring means comprises an AC resistance bridge. In the magnetization measuring apparatus using the SQUID element as a detector , a shunt resistor is connected in series between the output terminal of the superconducting magnet excitation power source and the superconducting magnet, and the magnetic field is read from the potential difference of the shunt resistor connecting portion. An apparatus for measuring electric resistance and Hall effect in a magnetic field using a magnetization measuring apparatus using the SQUID element according to claim 1 as a detector .

Images