JP2011112490A - Magnetization measuring device and measurement rod thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform measurement while controlling a carrier concentration by a magnetization measuring device. <P>SOLUTION: In the magnetization measuring device 1 provided with temperature adjusting means 10 and 16, magnetic field generating means 8 and 13, and a magnetic sensor 14, and measuring magnetic susceptibility of a sample, the device includes a pair of electrodes 5 and 22 to which voltage is applied, and an electrolytic solution filling the gap between the electrodes 5 and 22, wherein the sample is disposed on one of the electrodes 5 and 22. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a magnetization measuring apparatus for measuring the characteristics of a superconducting material.

  Various materials are prepared in search of a superconducting material, and the magnetic susceptibility, electrical resistance, and the like of the prepared materials are measured (see Patent Document 1). In general, a high-temperature oxide superconductor realizes a superconducting state in a predetermined range of carrier concentration. For this reason, by preparing a plurality of samples having different carrier concentrations stepwise for a certain material and measuring the magnetic susceptibility or the like for each sample having a different carrier concentration, a carrier concentration suitable for the material is sought.

JP 2007-123194 A

  Conventionally, the element substitution method by chemical treatment has been adopted for the preparation of a sample used for magnetic susceptibility measurement. Therefore, there has been a problem that it takes a lot of labor to prepare a plurality of samples having different carrier concentrations in stages.

(1) The present invention is applied to a magnetization measuring device that includes a temperature adjusting means, a magnetic field generating means, and a magnetic sensor and measures the magnetic susceptibility of a sample, and a pair of electrodes to which a voltage is applied and an electrolyte solution that fills between the electrodes And the sample is disposed on one of the electrodes.
(2) The present invention is a measurement of a magnetization measuring apparatus having a cooling means with liquid helium, a superconducting magnet, a magnetic field generating means, a temperature adjusting means, and a magnetic field adjusting means, and measuring the magnetic susceptibility of a sample using a SQUID element as a detector Applicable to rods. And it has a pair of electrodes to which a voltage is applied and an electrolyte solution that fills between the electrodes, and the sample is arranged on one of the electrodes.

  According to the present invention, magnetization can be measured for one sample while controlling the carrier concentration.

It is a figure explaining the magnetization measuring apparatus by one embodiment of this invention. It is sectional drawing to which the rod for measurement was expanded. It is a flowchart explaining an example of a measurement process. It is a flowchart explaining an example of another measurement process. It is a flowchart explaining an example of another measurement process. It is a figure which illustrates a measurement result.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a diagram for explaining a magnetization measuring apparatus according to an embodiment of the present invention. In FIG. 1, a magnetization measuring apparatus 1 is described later after replacing a measuring rod of a known MPMS (Magnetic Property Measurement Systems: magnetization measuring apparatus, manufactured by Quantum Design, USA) with a measuring rod 5 according to the present embodiment. The connector 6, the voltmeter 11 and the voltage source 12 are added. The measuring rod 5 is a member for mounting a sample on the magnetization measuring apparatus 1.

  The magnetization measuring device 1 is a device that controls the temperature and magnetic field of a sample while cooling the superconducting magnet 13 and the SQUID element 14 with liquid helium, and measures the magnetic susceptibility, magnetization curve, and Meissner effect of the sample. . An opening 3 for inserting a sample is provided in a container 2 filled with liquid helium for cooling, and a measuring rod 5 fitted with a magnetic sample (high temperature superconductor) to be measured is inserted into and removed from the opening 3. It is configured. Then, the micro magnetic field generated by the sample attached to the inserted measuring rod 5 is detected by the SQUID element 14 to which the Josephson effect of the superconductor is applied.

  In addition to the measurement rod 5, the connector 6, the voltmeter 11, the voltage source 12, the container 2, the superconducting magnet 13, and the SQUID element 14, the magnetization measuring device 1 includes a magnetic field measuring unit 7, a magnetic field adjusting unit 8, The temperature measuring unit 9, the temperature adjusting unit 10, the control device 4, and the heater 16 are included. The magnetic field adjustment unit 8 generates a magnetic field in the sample space 15 in which the tip of the measuring rod 5 is located by flowing a current according to an instruction from the control device 4 to the superconducting magnet 13. The magnetic field measurement unit 7 measures the magnetic field generated by the magnetic field adjustment unit 8 and sends the measurement result to the control device 4. Specifically, the generated magnetic field is calculated by multiplying the current value flowing through the superconducting magnet 13 by the magnetic field adjusting unit 8 by a predetermined coefficient.

  The temperature adjustment unit 10 adjusts the sample space 15 to a predetermined temperature higher than the temperature of liquid helium by flowing a current according to an instruction from the control device 4 to the heater 16. The temperature measurement unit 9 measures the temperature of the sample space 15 based on a detection signal from a temperature sensor (not shown), and sends the measurement result to the control device 4. The voltage source 12 generates a DC voltage according to an instruction from the control device 4 and supplies a voltage to be applied to the sample of the measuring rod 5. The voltmeter 11 measures the voltage applied to the sample and sends the measurement result to the control device 4. The connector 6 connects the measuring rod 5 and the voltage source 12.

  The control device 4 is constituted by a personal computer, for example. The control device 4 controls the voltage applied to the sample, the temperature of the sample space 15, and the magnetic field of the sample space 15 based on the magnetization measurement program, while the sample is attached to the measurement rod 5 and inserted into the container 2. A minute magnetic field is detected, and this detection signal is input to perform measurement processing.

  FIG. 2 is an enlarged cross-sectional view of the tip of the measuring rod 5 located in the sample space 15. In FIG. 2, the wiring material 23 a and the wiring material 23 b to the measuring rod 5 are connected to the voltage source 12 (FIG. 1) via the connector 6. The cylindrical measuring rod 5 is constituted by a hollow mandrel made of brass, for example. The length is about 1m and the outer shape is about 4mm. A separator 21 is wound around the outer periphery of the measuring rod 5, and a thin-film conductor 22 with a sample attached thereto is wound around the separator 21. In this embodiment, the separator 21 is made of cigarette paper, and a powder sample is applied to the adhesive surface of the carbon tape to form a conductor 22, and the separator 21 is sandwiched between the outer periphery of the measuring rod 5 and the carbon tape. The carbon tape is wound in a cylindrical shape with the adhesive surface side (that is, the surface to which the sample is attached) facing the separator 21 side. The width of the conductor 22 is about 1 cm, and the distance between the outer circumference of the measuring rod 5 and the conductor 22 is about 1 mm.

  As the sample, for example, a crystal made of copper oxide or the like crushed in a mortar to have an average particle diameter of about 10 μm is used. The particle size may be uneven, but a smaller one is preferred. Further, an electrolyte solution (for example, a LiClO4 polycarbonate solution) is soaked in the gap between the outer periphery of the measuring rod 5 and the conductor 22. The electrolyte solution penetrates by capillary action, and the solution is held in the gap between the outer surface of the measuring rod 5 and the adhesive surface side of the conductor 22. The separator 21 passes ions ionized in the electrolyte solution, but does not pass a powder sample.

  The conductor 22 and the measuring rod 5 constitute electrodes, respectively, and a voltage is applied between them. Specifically, the wiring member 23 b is connected to the conductor 22, and the other end of the wiring member 23 b that passes through the measurement rod 5 is connected to the negative terminal of the voltage source 12 (FIG. 1) via the connector 6. . Further, the wiring member 23a is connected to the measuring rod 5, and the other end of the wiring member 23a is connected to the positive terminal of the voltage source 12 (FIG. 1) via the connector 6.

  A sealing material 25 is provided on the upper portion of the measuring rod 5 (on the connector 6 side) to prevent intrusion of external gas and moisture from the upper portion of the measuring rod 5 to the inside. Further, the protective case 24 is covered so as to cover the conductor 22 described above, and the case 24 is filled with helium gas, and then the gap between the case 24 and the measuring rod 5 is covered, so that the sample space 15 is covered. Prevent ingress of external gases and moisture. The reason why helium gas is filled is to eliminate moisture in the case.

  As described above, ions existing in the electrolyte solution can move through the filter medium such as the separator 21. By applying a voltage between the electrodes (conductor 22 and measuring rod 5), ions are adsorbed on the surface of the powder sample. Since the amount of ions adsorbed depends on the applied voltage, the concentration of ions attached to the powder sample can be controlled by changing the applied voltage. That is, the carrier concentration of the sample mounted on the magnetization measuring apparatus 1 can be controlled.

  In the present embodiment, as described above, the magnetic field measurement is performed by combining the electric field induction control method for controlling the carrier amount by changing the applied voltage and the magnetization measurement, and appropriately changing the carrier concentration without exchanging the sample.

<Measure temperature dependence of magnetic susceptibility while maintaining carrier concentration>
FIG. 3 is a flowchart for explaining an example of the measurement process according to the present embodiment. When measuring the temperature change of the magnetic susceptibility at a predetermined carrier concentration, the control device 4 activates a program for performing the process illustrated in FIG. In step S10 of FIG. 3, the control device 4 determines whether or not the temperature range is programmed. When the temperature range to be measured is set, the control device 4 makes a positive determination in step S10 and proceeds to step S20. When the temperature range to be measured is not set, the control device 4 displays a message for prompting the setting of the temperature range on a monitor (not shown) and repeats the determination process.

  In step S20, the control device 4 sends an instruction to the voltage source 12, sets the applied voltage between the electrodes, that is, the sample to a predetermined value, and proceeds to step S30. Thereby, the carrier concentration of the sample is maintained at a concentration corresponding to the applied voltage.

  In step S30, the control device 4 sends an instruction to the temperature adjusting unit 10, sets the temperature of the sample space 15 to the programmed temperature, and proceeds to step S40. In step S40, the control device 4 sends an instruction to the magnetic field adjustment unit 8 and the magnetic field measurement unit 7, measures the magnetic susceptibility, and proceeds to step S50.

  In step S50, the control device 4 determines whether or not the measurement has been completed in the entire temperature range. When the measurement in the programmed temperature range is finished, the control device 4 makes a positive determination in step S50 and finishes the process shown in FIG. If the measurement in the programmed temperature range is not finished, the control device 4 makes a negative determination in step S50 and returns to step S30. When returning to step S30, it sets to the next temperature and repeats the process mentioned above.

<Measure the carrier concentration dependence of magnetic susceptibility while maintaining temperature>
FIG. 4 is a flowchart illustrating an example of another measurement process according to this embodiment. When measuring the carrier concentration dependence of the magnetic susceptibility at a predetermined temperature, the control device 4 activates a program for performing the process illustrated in FIG. In step S110 of FIG. 4, the control device 4 determines whether or not the voltage range is programmed. When the carrier concentration range to be measured (that is, the voltage range to be applied) is set, the control device 4 makes a positive determination in step S110 and proceeds to step S120. When the carrier concentration range to be measured (that is, the voltage range to be applied) is not set, the control device 4 displays a message prompting the setting of the voltage range on a monitor (not shown) and repeats the determination process.

  In step S120, the control device 4 sends an instruction to the temperature adjustment unit 10, sets the sample space 15 to a predetermined temperature, and proceeds to step S130. Thereby, the sample is maintained at a predetermined temperature.

  In step S130, the control device 4 sends an instruction to the voltage source 12, sets the voltage applied to the sample to the programmed voltage value, and proceeds to step S140. In step S140, the control device 4 sends an instruction to the magnetic field adjustment unit 8 and the magnetic field measurement unit 7, measures the magnetic susceptibility, and proceeds to step S150.

  In step S150, the control device 4 determines whether or not the measurement has been completed in the entire voltage range. When the measurement in the programmed voltage range is finished, the control device 4 makes an affirmative decision in step S150 and finishes the process shown in FIG. If the measurement in the programmed voltage range is not completed, the control device 4 makes a negative determination in step S150 and returns to step S130. When returning to step S130, it sets to the next applied voltage and repeats the process mentioned above.

<Measure temperature dependence of magnetic susceptibility while changing carrier concentration>
FIG. 5 is a flowchart illustrating an example of still another measurement process according to the present embodiment. When the temperature dependence of the magnetic susceptibility is measured while changing the carrier concentration, the control device 4 activates a program for performing the process illustrated in FIG. In step S10A of FIG. 5, the control device 4 determines whether the temperature range and the voltage range are programmed. When the temperature range to be measured is set and the carrier concentration range to be measured (that is, the voltage range to be applied) is set, the control device 4 makes a positive determination in step S10A and proceeds to step S130. When the temperature range to be measured or the carrier concentration range to be measured (that is, the voltage range to be applied) is not set, the control device 4 displays a message for prompting the setting on a monitor (not shown) and repeats the determination process.

  In step S130, the control device 4 sends an instruction to the voltage source 12, sets the voltage applied to the sample to the programmed voltage value, and proceeds to step S30.

  In step S30, the control device 4 sends an instruction to the temperature adjusting unit 10, sets the temperature of the sample space 15 to the programmed temperature, and proceeds to step S40. In step S40, the control device 4 sends an instruction to the magnetic field adjustment unit 8 and the magnetic field measurement unit 7, measures the magnetic susceptibility, and proceeds to step S50.

  In step S50, the control device 4 determines whether or not the measurement has been completed in the entire temperature range. When the measurement in the programmed temperature range is finished, the control device 4 makes a positive determination in step S50 and proceeds to step S60. If the measurement in the programmed temperature range is not finished, the control device 4 makes a negative determination in step S50 and returns to step S30. When returning to step S30, it sets to the next temperature and repeats the process mentioned above.

  In step S60, the control device 4 determines whether or not the measurement has been completed in the entire voltage range. When the measurement in the programmed voltage range is finished, the control device 4 makes a positive determination in step S60 and finishes the process shown in FIG. If the measurement in the programmed voltage range is not completed, the control device 4 makes a negative determination in step S60 and returns to step S130. When returning to step S130, it sets to the next applied voltage and repeats the process mentioned above.

  FIG. 6 is a diagram illustrating a measurement result obtained by the magnetization measuring apparatus 1. The horizontal axis represents the temperature of the sample, and the vertical axis represents the magnetic susceptibility. In general, when a superconducting transition occurs, the magnetic susceptibility fluctuates stepwise. In the development of new materials as superconducting materials, it is unclear whether or not electronic phase transitions will occur if a superconducting material is created at that carrier concentration after identifying the carrier concentration at which such electronic phase transitions occur. Compared with the case where many materials having different carrier concentrations are produced step by step, it is extremely effective in reducing labor and time.

According to the embodiment described above, the following operational effects can be obtained.
(1) Since the configuration is such that the carrier concentration of a sample to be measured for magnetization is controlled by electric field induction, the magnetization measurement for samples having different carrier concentrations can be performed without replacing the sample set in the magnetization measuring apparatus 1. Further, unlike the case where chemical treatment is performed, the influence of the disorder of the crystal structure is not included, so that a complicated electronic phase transition does not appear.

(2) Since the sample to be measured is pulverized and powdered, the specific surface area of the sample is increased. Thereby, since the sensitivity in magnetization measurement increases, the usage-amount of a sample is restrained to a small quantity.
(3) Since the powdered sample is attached to the adhesive surface of the conductor 22, it is possible to prevent the sample from being liberated.

(4) Since the capillary phenomenon is caused by narrowing the space between the electrodes and the electrolyte solution stays between the electrodes, the electrolyte solution can be suppressed to a small amount.
(5) Since the separator 21 is sandwiched between the electrodes, it helps to prevent a short circuit between the narrowed electrodes.

(6) Since the circumference of the surface of the rod-like metallic measuring rod 5 is covered with the annular conductor 22, it can be applied to a narrow sample space 15 as compared with the case where it is constituted by parallel plate electrodes.
(7) The measuring rod 5 having the above (1) to (6) is configured in the same size as the standard measuring rod of MPMS that is commercially available and widely used, and is mounted instead of the standard measuring rod. Since the configuration is possible, the entire magnetization measuring device can be configured at a lower cost than when newly designed and manufactured.

(Modification 1)
As the electrolyte solution, it is more preferable to use, for example, an ionic liquid used in a lithium ion secondary battery (see JP 2009-21060). The reason for this is that a portion where charges are concentrated can be created by generating an electric double layer. That is, when a voltage is applied between the electrodes, ion movement occurs in the ionic liquid, and both charge layers (electric double layers) in which positive and negative ions are accumulated appear at the interface between the ionic liquid, the powder sample, and the conductor 22. Since the distance of this electric double layer is close to about 1 nm, a large electric field can be obtained even when a low voltage is applied, so that the carrier concentration can be changed efficiently.

(Modification 2)
In FIG. 3, the direction in which the temperature is changed may be changed from the low temperature side to the high temperature side, or may be changed from the high temperature side to the low temperature side. Alternatively, measurement may be performed when changing from both directions, and the results of both measurements may be collated. The same applies to the case of FIG.

(Modification 3)
In FIG. 4, the direction in which the applied voltage is changed may be changed from the low voltage side to the high voltage side, or may be changed from the high voltage side to the low voltage side. Alternatively, measurement may be performed when changing from both directions, and the results of both measurements may be collated. The same applies to the case of FIG.

  When the temperature of the sample space 15 is changed, when the electrolyte solution such as an ionic liquid is solidified, the carrier concentration does not change even if the applied voltage is changed. For this reason, when it is desired to change the carrier concentration at a temperature lower than the temperature at which the electrolyte solution solidifies, the applied voltage is changed after the temperature of the sample space 15 is raised to melt the electrolyte solution. Then, the process of lowering the temperature of the sample space 15 to the original temperature after the voltage change is repeated.

(Modification 4)
As an example of the electrode configuration, the configuration example in which the circumference of the measuring rod 5 is annularly covered with the conductor 22 has been described. However, if the electrode can be inserted into the sample space 15, the electrode of the above embodiment is replaced with a flat plate. Also good. In the case of a plate electrode, a plate electrode with a separator sandwiched between electrode plates is immersed in the electrolyte solution. Needless to say, the electrolyte solution may be soaked and held between the two electrodes by capillary action.

(Modification 5)
An example in which cigarette paper is used as the separator 21 and the electrolyte solution is held in the gap between the outer surface of the measuring rod 5 and the conductor 22 by capillary action has been described. Instead, a separator having both ion permeability and electrolyte solution retention, such as a separator used in a general battery, can be used.

  The above description is merely an example, and is not limited to the configuration of the above embodiment. The size and configuration of the measuring rod 5, the size and configuration of the conductor 22, and the type of the electrolyte solution may not be as described above. Moreover, although the example which distribute | arranges a magnetic sample to the negative electrode side was demonstrated in the said embodiment, it can also be set as the structure distribute | arranged to the positive electrode side.

DESCRIPTION OF SYMBOLS 1 ... Magnetization measuring apparatus 2 ... Container 3 ... Opening 4 ... Control apparatus 5 ... Measuring rod 6 ... Connector 7 ... Magnetic field measurement part 8 ... Magnetic field adjustment part 9 ... Temperature measurement part 10 ... Temperature adjustment part 11 ... Voltmeter 12 ... Voltage Source 13 ... Superconducting magnet 14 ... SQUID element 16 ... Heater 21 ... Separator 22 ... Conductors 23a, 23b ... Wiring material 24 ... Case 25 ... Sealing material

Claims (8)

In a magnetization measuring apparatus that includes a temperature adjusting means, a magnetic field generating means, and a magnetic sensor and measures the magnetic susceptibility of a sample,
A pair of electrodes to which a voltage is applied;
An electrolyte solution filling between the electrodes,
A magnetization measuring apparatus, wherein the sample is disposed on one of the electrodes. The magnetization measuring apparatus according to claim 1,
The electrode is applied with a DC voltage,
The sample is arranged on the positive electrode side or the negative electrode side of the electrode and immersed in the electrolyte solution. The magnetization measuring apparatus according to claim 2, wherein
The magnetization measuring apparatus, wherein the sample is powdered. The magnetization measuring apparatus according to claim 3.
The powder measurement sample is attached to a surface of the one electrode. In the magnetization measuring device according to any one of claims 2 to 4,
The distance between the pair of electrodes is a distance for holding the electrolyte solution between the electrodes by capillary action. In the magnetization measuring device according to any one of claims 2 to 5,
A magnetization measuring apparatus, wherein a separator is sandwiched between the pair of electrodes. In the magnetization measuring device according to any one of claims 1 to 6,
The magnetization measuring apparatus, wherein the electrolyte solution is an ionic liquid electrolyte. A measuring rod of a magnetization measuring apparatus that has a cooling means with liquid helium, a superconducting magnet, a magnetic field generating means, a temperature adjusting means, and a magnetic field adjusting means, and measures the magnetic susceptibility of a sample using a SQUID element as a detector,
A pair of electrodes to which a voltage is applied;
An electrolyte solution filling between the electrodes,
The measurement rod of a magnetization measuring apparatus, wherein the sample is disposed on one of the electrodes.

Images