Vibrating sample magnetometer and methods for measuring magnetic properties.

Abstract

Invention details;

Description

Vibrating sample magnetometer

[0001] The present disclosure relates to vibrating sample magnetometers.

[0002] A vibrating sample magnetometer vibrates a magnetic sample placed in a magnetic field at a constant frequency and amplitude, measures the electromotive force induced in a detection coil placed around the magnetic sample, and derives the magnetic properties of the magnetic sample based on the relationship between the electromotive force and the magnetic properties.Since the magnetic properties of magnetic samples deteriorate when an external load is applied, in the case of magnetic samples that operate under pressure, it is necessary to measure the magnetic properties while an external force is applied.

[0003] Patent Document 1 discloses a vibrating sample magnetometer that has a means for applying pressure to a measurement sample and a pressure measurement means for measuring the applied pressure, and is configured so that the measurement sample can be vibrated while pressure is being applied to the measurement sample.

[0004] JP 2018-84463 A

[0005] When a strong external magnetic field is applied to a magnetic sample while an external pressure is still being applied, the deteriorated magnetic properties are slightly restored. However, although it is possible to measure the magnetic properties while an external stress is still being applied to the measurement sample in Patent Document 1, the magnetic properties are restored because a strong external magnetic field is applied to the measurement sample during the magnetic field sweep. This poses a problem in that it is not possible to accurately measure the deterioration of the magnetic properties due to the application of external stress.

[0006] The present disclosure has been made in consideration of the above, and aims to provide a vibrating sample magnetometer that can accurately measure the deterioration of magnetic properties when external pressure is applied to a measurement sample.

[0007] In order to solve the above-mentioned problems and achieve the object, the presently disclosed vibrating sample magnetometer includes a sample-accommodating vibrator that accommodates a measurement sample and vibrates the measurement sample in one direction, an exciting electromagnet that applies an external magnetic field to the measurement sample, a pressure application unit that applies pressure to the measurement sample, a pressure acquisition unit that measures the applied pressure, a magnetic property acquisition unit that detects an induced voltage due to the vibration of the measurement sample magnetized by the exciting electromagnet and acquires magnetic properties that indicate the relationship between the magnetic flux density, which is the sum of the magnetization of the measurement sample and the external magnetic field, and the external magnetic field, and a control device that controls the external magnetic field and pressure and sweeps the external magnetic field. When acquiring magnetic properties with pressure applied to the measurement sample, the control device sets a first magnetic field value as a sweep start value and sweeps the external magnetic field with a magnetic field equal to or less than the first magnetic field value. The first magnetic field value is a value smaller than a second magnetic field value, which is a magnetic field value acquired before pressure is applied to the measurement sample and corresponds to the saturation magnetic flux density of the measurement sample in a pressure-free state.

[0008] The vibrating sample magnetometer of the present disclosure has the effect of enabling accurate measurement of the deterioration of magnetic properties when an external pressure is applied to a measurement sample.

[0009] FIG. 1 is a diagram showing an example of a schematic configuration of a vibrating sample magnetometer according to embodiment 1; FIG. 2 is a block diagram showing an example of a functional configuration of a control device for a vibrating sample magnetometer according to embodiment 1; FIG. 3 is a block diagram showing an example of a hardware configuration of a control device for a vibrating sample magnetometer according to embodiment 1; FIG. 4 is a process diagram showing an example of a measurement procedure for the vibrating sample magnetometer according to embodiment 1; FIG. 5 is a diagram showing magnetic properties obtained under the first measurement condition in an unloaded state according to embodiment 1; FIG. 6 is a diagram showing magnetic properties obtained under the second measurement condition in a loaded state according to embodiment 1;

[0010] Hereinafter, a vibrating sample magnetometer according to an embodiment will be described in detail with reference to the drawings.

[0011] 1 is a diagram showing a schematic configuration example of a vibrating sample magnetometer 100 according to embodiment 1. The vibrating sample magnetometer 100 includes a sample-accommodating vibrator 1, a support table 2, a vibration device 3, an external force application mechanism 4, a magnetic property imparting and measuring unit 5, a temperature-controlled gas supply pipe 7, a temperature-controlled gas supply device 8, and a control device 10.

[0012] The sample-accommodating vibrating body 1 vibrates in one direction. In this case, the sample-accommodating vibrating body 1 vibrates up and down. The sample-accommodating vibrating body 1 has a hollow cylindrical sample storage section 1a in which a measurement sample S is stored, and a pressure application rod 1b that is inserted into the sample storage section 1a and applies pressure to the measurement sample S. The sample-accommodating vibrating body 1 is provided with a temperature detection section 1c that detects the temperature of the measurement sample S. The temperature of the measurement sample S detected by the temperature detection section 1c is input to the control device 10. The sample-accommodating vibrating body 1 is also provided with a vibration detection section (not shown) that detects the vibration state including the frequency and amplitude of the vibration of the sample-accommodating vibrating body 1. The vibration state of the sample-accommodating vibrating body 1 detected by the vibration detection section is input to the control device 10.

[0013] The vibration device 3 vibrates the sample-accommodating vibrating body 1 up and down. The support base 2 is a base for fixing the vibration device 3. The vibration device 3 vibrates the sample-accommodating vibrating body 1 up and down based on a vibration frequency and amplitude specified by the control device 10.

[0014] The external force application mechanism 4 is connected to the pressure application rod 1b of the sample accommodation vibrating body 1, and applies an external force to the measurement sample S by applying an external force to the pressure application rod 1b. The external force application mechanism 4 has a pressure detection unit 4a. The pressure detection unit 4a is, for example, a load cell. The load cell uses a strain gauge to convert the force into an electrical signal. The pressure detection unit 4a detects the pressure applied to the measurement sample S by measuring the pressure received by the pressure application rod 1b from the measurement sample S. The pressure applied to the measurement sample S, detected by the pressure detection unit 4a, is input to the control device 10.

[0015] The magnetic property imparting and measuring unit 5 has an exciting electromagnet 5a that imparts an external magnetic field to the measurement sample S, and a detection coil 5b that detects an induced voltage due to vibration of the measurement sample S magnetized by the exciting electromagnet 5a. The detection coil 5b is disposed near the measurement sample S. The induced voltage detected by the detection coil 5b is input to the control device 10.

[0016] The temperature control gas supply device 8 supplies a temperature control gas for controlling the temperature of the measurement sample S to the vicinity of the measurement sample S accommodated in the sample accommodation vibrating body 1 via the temperature control gas supply pipe 7. By spraying the temperature control gas onto the measurement sample S, the measurement sample S can be heated or cooled. The temperature of the temperature control gas is controlled by the control device 10.

[0017] In this configuration, the measurement sample S is placed at the tip of the sample storage section 1a of the sample-accommodating vibrator 1. The temperature of the measurement sample S is detected by the temperature detection section 1c of the sample-accommodating vibrator 1. The temperature of the measurement sample S is adjusted by temperature-control gas supplied from the temperature-control gas supply device 8. The pressure application rod 1b is inserted into the sample storage section 1a, and the measurement sample S is fixed to the sample storage section 1a by the pressure application rod 1b. In this state, the sample-accommodating vibrator 1 is vibrated vertically by the vibration device 3. This vibration state is detected by a vibration detection section (not shown). Pressure is applied to the measurement sample S in the same direction as the vibration direction by the external force application mechanism 4 and the pressure application rod 1b. When pressure acts on the measurement sample S, a counterforce acts on the pressure application rod 1b in the opposite direction. The pressure acting on the pressure application rod 1b is detected by the pressure detection section 4a of the external force application mechanism 4. An induced voltage is generated in the measurement sample S due to the vibration. This induced voltage is detected by the detection coil 5b of the magnetic property imparting and measuring section 5. An external magnetic field is applied to the measurement sample S by the exciting electromagnet 5a, and the measurement sample S is magnetized.

[0018] The control device 10 controls the vibration device 3, the external force application mechanism 4, the magnetic property imparting and measuring unit 5, and the temperature-controlled gas supply device 8. Fig. 2 is a block diagram showing an example of the functional configuration of the control device 10 of the vibrating sample magnetometer 100 of embodiment 1. The control device 10 includes a main control unit 11, a magnetic property acquisition unit 12, a temperature acquisition unit 13, a pressure acquisition unit 14, a vibration control unit 15, a temperature control unit 16, a pressure control unit 17, an external load environment determination unit 18, and an external magnetic field sweep unit 19.

[0019] The magnetic property acquisition unit 12 calculates magnetic properties indicating the correspondence between the magnetic flux density B, which is the sum of the magnetization of the measurement sample S and the external magnetic field, and the external magnetic field (magnetic field) H, based on the magnetization measurement results of the measurement sample S obtained from the detection coil 5b, and sends the calculated magnetic properties to the main control unit 11.

[0020] The temperature acquisition unit 13 calculates the temperature T of the measurement sample S based on the temperature detection result of the measurement sample S obtained from the temperature detection unit 1 c, and sends the calculated temperature T to the main control unit 11.

[0021] The pressure acquisition unit 14 calculates the external pressure (pressure) P applied to the measurement sample S based on the pressure detection result of the measurement sample S detected by the pressure detection unit 4a, and sends the calculated external pressure P to the main control unit 11.

[0022] The vibration control unit 15 controls the vibration device 3. The vibration control unit 15 controls the vibration device 3 by feeding back the vibration state of the sample housing vibration body 1 acquired from a vibration detection unit (not shown), and controls the vibration frequency, amplitude, vibration start time, and vibration end time of the up and down vibration of the sample housing vibration body 1.

[0023] The temperature control unit 16 acquires the temperature T of the measurement sample S calculated by the temperature acquisition unit 13 from the main control unit 11. The temperature control unit 16 controls the temperature-controlled gas supply device 8 by feeding back the temperature T of the measurement sample S, and controls the temperature of the temperature-controlled gas supplied from the temperature-controlled gas supply device 8.

[0024] The pressure control unit 17 acquires the pressure P to be applied to the measurement sample S, calculated by the pressure acquisition unit 14, from the main control unit 11. The pressure control unit 17 controls the external force application mechanism 4 by feeding back the pressure P to be applied to the measurement sample S, and controls the pressure application rod 1b so that the specified pressure P is applied to the measurement sample S.

[0025] The external load environment determination unit 18 derives the sweep start value Hs and sweep end value He of the external magnetic field H based on the measurement results of the magnetic properties indicating the correspondence between the magnetic flux density B and the external magnetic field H, and transmits them to the main control unit 11.

[0026] The external magnetic field sweep unit 19 acquires the sweep start value Hs and sweep end value He of the external magnetic field H from the main control unit 11. The external magnetic field sweep unit 19 transmits the sweep start value Hs and sweep end value He of the external magnetic field H to the exciting electromagnet 5a to control the sweep of the exciting electromagnet 5a.

[0027] The main control unit 11 controls each functional unit by sending a control signal to each functional unit based on information acquired from each functional unit, including the magnetic property acquisition unit 12, the temperature acquisition unit 13, the pressure acquisition unit 14, the vibration control unit 15, the temperature control unit 16, the pressure control unit 17, the external load environment determination unit 18, and the external magnetic field sweep unit 19.

[0028] 3 is a block diagram showing an example of the hardware configuration of the control device 10 of the vibrating sample magnetometer 100 of the first embodiment. The control device 10 can be realized by a processor 101, a memory 102, and an interface circuit 103 shown in FIG. 3. Examples of the processor 101 include a CPU (Central Processing Unit, also referred to as a central processing unit, processing device, arithmetic unit, microprocessor, microcomputer, or DSP (Digital Signal Processor)) or a system LSI (Large Scale Integration). Examples of the memory 102 include a RAM (Random Access Memory) and a ROM (Read Only Memory).

[0029] The control device 10 is realized by the processor 101 reading and executing a program for executing the operation of the control device 10, which is stored in the memory 102. This program can also be said to cause a computer to execute the procedure or method of the control device 10. The memory 102 is also used as temporary memory when the processor 101 executes various processes. Note that some of the functions of the control device 10 may be realized by dedicated hardware and some by software or firmware.

[0030] It is known that the magnetic properties of a measurement sample S, which is a magnetic material, are degraded when pressure is applied from the outside. On the other hand, the present inventors have newly discovered that when pressure (stress) is applied from the outside to the measurement sample S and a strong external magnetic field is applied to the measurement sample S in a state in which the magnetic properties are degraded, some or all of the degraded magnetic properties are restored. In this way, when an excessively strong external magnetic field is applied to the measurement sample S while pressure is still being applied from the outside, some or all of the degraded magnetic properties are restored.

[0031] In the vibrating sample magnetometer of Patent Document 1, when measuring the magnetic properties of a measurement sample S with pressure applied thereto, the magnetic properties are acquired by sweeping the external magnetic field toward a stronger magnetic field and then toward a weaker magnetic field while pressure is applied to the measurement sample S. However, this method does not accurately acquire the magnetic properties that have been reduced by applying external pressure to the measurement sample S, and only acquires the magnetic properties after some or all of the magnetic properties that have been reduced by applying pressure have been restored.

[0032] In products equipped with magnetic materials, such as motors, the magnetic properties deteriorate due to the effects of stress caused by centrifugal force when the motor rotates, but general motors do not have a mechanism to restore deteriorated magnetic properties. Therefore, unless the magnetic properties of magnetic materials that have deteriorated due solely to the effects of stress can be accurately grasped, it is impossible to accurately evaluate the motor performance of motors in use.

[0033] Therefore, in order to accurately grasp the state of deterioration of the magnetic properties due to the influence of stress, the vibrating sample magnetometer 100 of embodiment 1 determines a magnetic field at which the magnetic properties that have been deteriorated by the application of external pressure will not recover as a sweep start value Hs, and applies a magnetic field equal to or less than the determined sweep start value Hs to the measurement sample S to sweep the magnetic field.

[0034] In the vibrating sample magnetometer 100 of the first embodiment, the following measurement is carried out, for example, to accurately grasp the state of deterioration of magnetic properties due to the influence of pressure. Figure 4 is a process diagram showing an example of a measurement procedure for the vibrating sample magnetometer 100 of the first embodiment.

[0035] First, the vibration control unit 15 controls the vibration device 3 to set the sample housing vibrator 1 to vibrate up and down at a specified vibration frequency and amplitude. The temperature control unit 16 controls the temperature-controlled gas supply device 8 to adjust the temperature T of the measurement sample S to T0. T0 is set to, for example, 25°C. The pressure control unit 17 controls the external force application mechanism 4 to set the pressure P applied to the measurement sample S to an unloaded state (pressure P = P0 = 0 MPa). In this way, the control device 10 sets the measurement conditions of the measurement sample S to the first measurement condition (P0, T0) of an unloaded state. After this, the external magnetic field sweep unit 19 controls the exciting electromagnet 5a to perform full-loop magnetic field sweep control, applying an external magnetic field (magnetic field) H to the measurement sample S in its initial state. The magnetic property acquisition unit 12 acquires the full-loop magnetic properties of the measurement sample S generated by the magnetic field sweep control based on the magnetization measurement results of the measurement sample S obtained from the detection coil 5b (step S100). An initial measurement sample is a measurement sample to which no load has been previously applied.

[0036] 5 is a diagram showing the magnetic characteristics (B-H loop) obtained under the first measurement condition (P0, T0) in an unloaded state in embodiment 1. In FIG. 5, the vertical axis represents the magnetic flux density B (unit: tesla), and the horizontal axis represents the magnetic field H (unit: A / m). The magnetic characteristics under these measurement conditions are generally values ​​listed in a catalog for magnetic materials.

[0037] Full-loop magnetic field sweep control under the first measurement conditions (P0, T0) is performed as follows. First, an external magnetic field H is applied to the measurement sample S in its initial state, increasing from H=0 to the positive limit value Hlmt of the exciting electromagnet 5a and detection coil 5b of the magnetic property assigning and measuring unit 5, which is a measuring instrument. This magnetizes the measurement sample S, and the magnetic flux density B increases along line L1 from the origin O, where B=0, to point C1, where the saturation magnetic flux density Bs is reached. The magnetic field H corresponding to the saturation magnetic flux density Bs is also referred to as the maximum magnetizing force Hmax. The maximum magnetizing force Hmax in the magnetic properties obtained under the first measurement conditions (P0, T0) in a no-load state corresponds to the second magnetic field value in the claims.

[0038] Next, an external magnetic field H that decreases from the positive limit value Hlmt to H = 0 is applied to the measurement sample S. This demagnetizes the measurement sample S, and the magnetic flux density B decreases along the line L2 from point C1 where B = Bs to the residual magnetic flux density Br.

[0039] Next, the external magnetic field H is reversed, and an external magnetic field H that increases from H=0 to the negative limit value −Hlmt of the measuring device is applied to the measurement sample S. As a result, the magnetic flux density B changes along the line L3 from the residual magnetic flux density Br to the coercive force H at which B=0. ＣＢ BHmax is the maximum energy product, which is the point on the demagnetization curve where the product of the magnetic flux density B and the magnetic field H is the maximum value.

[0040] Next, an external magnetic field H is applied to the measurement sample S, decreasing from the negative limit value −Hlmt to H = 0. This demagnetizes the measurement sample S, and the magnetic flux density B decreases along line L4 from point C2 where B = −Bs to a residual magnetic flux density −Br.

[0041] Next, the external magnetic field H is reversed, and an external magnetic field H that increases from H=0 to the positive limit value Hlmt of the measuring device is applied to the measurement sample S. As a result, the magnetic flux density B changes along the line L5 from the residual magnetic flux density −Br to the coercive force H at which B=0. ＣＢ and increases to point C1 where the saturation magnetic flux density is Bs.

[0042] FIG. 6 shows the magnetic characteristics (B-H loop) obtained under the second measurement condition (P1, T0) under a load in the first embodiment. The dashed line L2 in FIG. 6 corresponds to the line L2 under the no-load condition in FIG. 5. Next, the control device 10 controls the temperature-controlled gas supply device 8, the external force application mechanism 4, and the magnetic property assigning and measuring unit 5 to apply an external magnetic field H to the measurement sample S from H=0 to the positive limit value Hlmt of the measuring device while the measurement condition of the measurement sample S is set to the first measurement condition (P0, T0) under the no-load condition. As a result, the magnetic characteristics shown by the line Q1 in FIG. 6 are obtained.

[0043] Next, the control device 10 sets the measurement conditions for the measurement sample S to second measurement conditions (P1, T0) under a load. For example, the pressure P1 is set to 100 MPa and the temperature T0 is set to 25°C. The external load environment determination unit 18 of the control device 10 sets the sweep start value Hs of the external magnetic field H to H=0 and the sweep end value He of the external magnetic field H to the negative limit value −Hlmt described above. The control device 10 then executes sweep control after the temperature T and pressure P of the measurement sample S have stabilized. This allows sweep control of the external magnetic field H to be performed while an external load is applied to the measurement sample S. According to the magnetic field sweep control from H=0 to the negative limit value −Hlmt under the second measurement conditions (P1, T0), the first quadrant of the magnetic characteristics is skipped, as indicated by arrow 30 in FIG. 6 . Furthermore, a demagnetization curve, which represents the magnetic characteristics in the second and third quadrants, is acquired (step S110), as indicated by line Q2.

[0044] When acquiring the magnetic characteristics under the loaded condition under the second measurement conditions (P1, T0), it is necessary to provide an external magnetic field that does not cause the magnetic characteristics to recover as the sweep start value Hs. Under the second measurement conditions (P1, T0), the maximum value of the external magnetic field that does not cause the magnetic characteristics to recover has not yet been determined, so the simplest method of setting the sweep start value Hs to H = 0 is adopted. Therefore, as long as the external magnetic field is such that the magnetic characteristics do not recover, an external magnetic field greater than H = 0 may be set as the sweep start value Hs.

[0045] Next, the external load environment determination unit 18 of the control device 10 calculates the difference ΔB1 between the magnetic properties under the first measurement condition (P0, T0) and the magnetic properties under the second measurement condition (P1, T0) (step S120). This difference ΔB1 makes it possible to grasp the demagnetization characteristics when pressure (stress) is applied to the measurement sample S.

[0046] FIG. 7 shows the magnetic characteristics obtained when the load on the measurement sample S is removed after a load is applied in the first embodiment. The dashed line L2 in FIG. 7 corresponds to the line L2 in FIG. 5 . After acquiring the magnetic characteristics under the second measurement conditions (P1, T0), the control device 10 resets the measurement conditions for the measurement sample S to the third measurement conditions (P0′, T0) under an unloaded state. For example, the pressure P0 is set to 0 MPa and the temperature T0 is set to 25°C. This third measurement condition is the same as the first measurement condition in terms of the pressure P and temperature T, but differs from the first measurement condition in that the load is applied to the measurement sample S and then removed. Therefore, this third measurement condition is referred to as the third measurement condition, and the pressure P is written as P0′. Furthermore, the control device 10 performs full-loop magnetic field sweep control (step S130) by controlling the exciting electromagnet 5a to apply an external magnetic field H to the measurement sample S, as described in FIG. 5 . That is, the external magnetic field is swept from H=0 to the positive limit value Hlmt, then from the positive limit value Hlmt to the negative limit value −Hlmt, and then from the negative limit value −Hlmt to the positive limit value Hlmt. By performing the magnetic field sweep control again under this third measurement condition (P0′, T0), it is possible to obtain a full B-H loop when the stress on the measurement sample S is released, as shown in FIG.

[0047] Now let's consider the coercive force of a magnet. There are many crystal grains inside a magnet, and these crystal grains have a magnetic domain structure. Neodymium magnets are manufactured by compressing and sintering magnet powder, but immediately after manufacturing they have no coercive force and do not exhibit magnetic properties. When a magnetic field is applied to the magnet from an external coil, etc., the magnetic domain orientation of the crystal grains aligns in one direction, thereby exhibiting magnetic properties and becoming what is known as a magnet. Since magnetic properties are the sum of the magnetic domain structures of the crystal grains, the more crystal grains there are with magnetic domain structures that are aligned in one direction, the higher the magnetic properties will be.

[0048] The weakening of a magnet's magnetic properties, or demagnetization, can occur when the magnetic domain orientation of some crystal grains changes from a state in which they were aligned in one direction to a state in which the magnetic domain orientation of some crystal grains changes to a different direction, or when the magnetic domains themselves become multiple magnetic domains (multi-domain structure). To align the magnetic domain orientations of randomly oriented crystal grains in one direction, it is necessary to apply a magnetic field to the magnet from an external source, such as an external coil. Applying a magnetic field to the magnet from an external source can sometimes restore the magnetic domains of crystal grains that have become aligned in a different direction or have become multi-domain structures, which are aligned in only one direction, to a single-domain structure (reversible demagnetization). On the other hand, external loads such as stress can cause the magnetic domain orientation to change to a different direction, or the magnetic domain structure of crystal grains that have become multi-domain structures can become aligned in different directions, and no longer return to a single-domain structure (irreversible demagnetization).

[0049] Here, let us consider the demagnetization of the magnetic properties when pressure is applied to the measurement sample S. As explained above, there are two types of demagnetization of magnets: reversible and irreversible. In reversible demagnetization, when a magnetic field is applied again from the outside to the measurement sample S, the magnetic domain structure is aligned and the magnetic properties are reproduced. In other words, in reversible demagnetization, the sample recovers from the demagnetized state. On the other hand, in irreversible demagnetization, when a magnetic field is applied again from the outside to the measurement sample S, the magnetic domain structure does not align and the magnetic properties are not reproduced. In other words, in irreversible demagnetization, the sample does not recover from the demagnetized state. The demagnetization of the magnetic properties when stress is applied to the measurement sample S includes both reversible and irreversible demagnetization.

[0050] The external load environment determination unit 18 of the control device 10 calculates the difference ΔB2 between the magnetic properties under the first measurement condition (P0, T0) and the magnetic properties under the third measurement condition (P0', T0) (step S140). This makes it possible to detect the difference ΔB2 between the magnetic properties before and after the application of pressure to the measurement sample S. If this difference ΔB2 is present, it can be confirmed that the change in the magnetic properties due to the application of pressure to the measurement sample S is an irreversible change.

[0051] The external load environment determination unit 18 of the control device 10 also acquires the saturation magnetic flux density Bs (see FIG. 7) of the magnetic characteristics under the third measurement condition (P0', T0), and further acquires the magnetic field value H1 (see FIG. 7) corresponding to this saturation magnetic flux density Bs. Furthermore, the external load environment determination unit 18 of the control device 10 selects a first magnetic field value Ha, which is an arbitrary magnetic field value, from the external magnetic field H where H≦H1, and determines the selected first magnetic field value Ha as the sweep start value Hs for acquiring the magnetic characteristics in a loaded state (step S150). That is, the external load environment determination unit 18 of the control device 10 sets the first magnetic field value Ha, which is a magnetic field value having a value equal to or less than the magnetic field value H1 corresponding to the saturation magnetic flux density Bs of the magnetic characteristics in an unloaded state, as the sweep start value Hs.

[0052] In this way, once the sweep start value Hs for acquiring the magnetic properties under load is determined to be the first magnetic field value Ha, the control device 10 performs a magnetic field sweep using the determined sweep start value Hs (= Ha) to acquire the magnetic properties of the measurement sample S under load (step S160). For example, in FIG. 6, the sweep start value Hs is set to H = 0, but the sweep start value Hs can be set to H = Ha to acquire the magnetic properties under load in the same manner as in FIG. 6. As a result, if the first magnetic field value Ha is set to a value that allows acquisition of the magnetic properties of the first quadrant, the magnetic properties of the first quadrant can also be acquired. Furthermore, when acquiring the magnetic properties under load from the third quadrant via the fourth quadrant back to the first quadrant, the sweep end value He can be set to H = Ha. Furthermore, if magnetic properties including the magnetic properties of the first quadrant of another measurement sample S made of the same material are to be obtained thereafter, the sweep start value Hs in step S110 can be set to H = Ha, the procedure can be ended at step S120, and the processing of steps S130 to S160 can be omitted.

[0053] As described above, in the first embodiment, after pressure P is applied to the measurement sample S, the applied pressure P is released, the magnetic characteristics in the pressure P-released state are obtained, the first magnetic field value Ha having a value equal to or less than the magnetic field value H1 corresponding to the saturation magnetic flux density Bs in the magnetic characteristics in the pressure P-released state is set as the sweep start value Hs, and the magnetic characteristics (B-H characteristics) of the measurement sample S starting from the sweep start value Hs are obtained. Therefore, a strong magnetic field is not applied to the measurement sample S from the outside during the magnetic field sweep, and it is possible to accurately measure the deterioration of the magnetic characteristics due to the application of external stress. This makes it possible to accurately estimate the deterioration state of the magnetic characteristics of magnetic materials mounted on motor devices, etc.

[0054] Embodiment 2. Consider the demagnetizing field of the measurement sample S. A magnetized magnetic body also creates a magnetic field inside the body. A magnet has two magnetic poles, a north pole and a south pole, and magnetic flux exits the magnet from the north pole and returns to the south pole. However, in addition to the magnetic flux leaking out to the outside, there is also magnetic flux inside the magnet that flows from the north pole to the south pole. Because the direction of the magnetic flux inside the magnet is opposite to the direction of the magnetic flux returning from outside the magnet, this type of magnetic field is called a demagnetizing field.

[0055] In order to accurately evaluate the magnetic properties of the measurement sample S, it is necessary to express them using a B-H loop that eliminates the effects of demagnetizing fields. However, with a vibrating sample magnetometer, which measures in an open magnetic circuit, the effects of demagnetizing fields must be corrected. If this is not done, the magnetic properties will not be evaluated accurately, unlike a B-H loop measured in a closed magnetic circuit that is not affected by demagnetizing fields.

[0056] Demagnetizing field correction technology is a method for creating a B-H loop that eliminates the effects of demagnetizing fields when measuring an open magnetic circuit. This is a technology that corrects a distorted B-H loop measured in an open magnetic circuit so that it has the same shape as a B-H loop measured in a closed magnetic circuit, and various methods exist.

[0057] One method of demagnetizing field correction is to use an algorithm to calculate the B-H loop of a closed magnetic circuit measurement from the B-H loop of an open magnetic circuit measurement. When applying this correction method, the more measurement points for the B-H characteristics in the first quadrant of the B-H loop, the higher the prediction accuracy of the B-H loop of a closed magnetic circuit measurement.

[0058] Therefore, in the second embodiment, in order to increase the number of measurement points for the BH characteristic in the first quadrant, measurements are carried out as follows. FIG. 8 is a process diagram showing an example of the measurement procedure for the vibrating sample magnetometer of the second embodiment. FIG. 9 is a diagram showing the magnetic characteristic (BH loop) obtained under the second measurement condition (P1, T0) in a loaded state in the second embodiment. The measurement procedure of the second embodiment will be explained below with reference to FIGS. 5, 8, and 9.

[0059] First, as described with reference to FIG. 5 , the control device 10 sets the measurement conditions for the measurement sample S in the initial state to the first measurement conditions (P0, T0) for the unloaded state described above. P0 = 0 MPa, T0 = 25°C. The control device 10 also controls the exciting electromagnet 5a to perform full-loop magnetic field sweep control, applying an external magnetic field H to the measurement sample S. That is, the external magnetic field is swept from H = 0 to the positive limit value Hlmt, from the positive limit value Hlmt to the negative limit value −Hlmt, and from the negative limit value −Hlmt to the positive limit value Hlmt. By performing magnetic field sweep control under this first measurement condition (P0, T0), a full-loop B-H loop such as that shown in FIG. 5 can be obtained (step S200).

[0060] Next, the control device 10 controls the temperature-controlled gas supply device 8, the external force application mechanism 4, and the magnetic property measurement unit 5 to apply an external magnetic field H from H=0 to the positive limit value Hlmt of the measurement device to the measurement sample S, while setting the measurement conditions of the measurement sample S to the first measurement conditions (P0, T0) of the no-load state. As a result, the magnetic properties shown by line G1 in Figure 9 are obtained.

[0061] Next, the control device 10 reduces the external magnetic field H to a magnetic field value H2, which is the sweep start value Hs. As indicated by arrow 31 in FIG. 9, this magnetic field value H2 is selected to be a value smaller than the maximum magnetizing force Hmax of the magnetic characteristics shown in FIG. 5 under the first measurement condition (P0, T0) in the no-load state previously measured. The maximum magnetizing force Hmax is the value of the magnetic field H corresponding to the saturation magnetic flux density (maximum magnetic flux density) Bs. Here, a value 5% lower than the maximum magnetizing force Hmax is selected as the magnetic field value H2. The control device 10 also sets the sweep end value He of the external magnetic field to the negative limit value -Hlmt.

[0062] Next, the control device 10 sets the measurement conditions of the measurement sample S to second measurement conditions (P1, T0) under a load. For example, the pressure is set to P1 = 100 MPa, and the temperature is set to T0 = 25°C. After the temperature and pressure of the measurement sample S have stabilized, the control device 10 executes magnetic field sweep control under this load state from the magnetic field value H2 to the sweep end value -Hlmt. This executes magnetic field sweep control from the magnetic field value H2 to the sweep end value -Hlmt with an external load applied to the measurement sample S. By executing magnetic field sweep control under this second measurement condition (P1, T0) from H = H2 to the negative limit value -Hlmt, a demagnetization curve representing the magnetic characteristics of the first quadrant, as shown by line G2 in FIG. 9, and a demagnetization curve representing the magnetic characteristics of the second and third quadrants, as shown by line G3, are acquired (step S210).

[0063] Next, the control device 10 calculates the difference ΔB3 between the magnetic properties under the first measurement condition (P0, T0) and the magnetic properties under the second measurement condition (P1, T0) (step S220). This difference ΔB3 makes it possible to grasp the demagnetization characteristics when stress is applied to the measurement sample S.

[0064] Here, when selecting the magnetic field value H2, it is desirable to select a different value depending on the demagnetization resistance of the measurement sample S due to an external load. For example, if the demagnetization resistance of the measurement sample S is low and the maximum magnetic field force Hmax1 indicated by the B-H characteristics when P1 = 100 MPa and T0 = 25°C is 7% demagnetized compared to the maximum magnetizing force Hmax in the no-load state, then the magnetic field value H2 should be selected to be at least 7% lower than the maximum magnetizing force Hmax, for example, 10%. The maximum magnetic field force Hmax1 is obtained from the demagnetization curve in the third quadrant, as shown in FIG. 9 . This is because selecting a magnetic field value H2 such that H2 > Hmax1 may result in the magnetic properties of the measurement sample S recovering, potentially preventing accurate evaluation of the demagnetization characteristics due to an external load.

[0065] In order to maximize the number of measurement points for the B-H characteristics in the first quadrant of the magnetization curve, it is desirable to set the magnetic field value H2 as large as possible within a range in which the magnetic characteristics of the measurement sample S are not restored. To achieve this, it is necessary to improve the accuracy of the selection of the magnetic field value H2 performed by the external load environment determination unit 18. To achieve this, it is effective to predict the magnetic field value H2 by referencing B-H characteristic data obtained by measuring a sample equivalent to the measurement sample S, and the prediction accuracy of this method can be improved by using machine learning.

[0066] In this way, in the second embodiment, the magnetic field sweep control is performed under a load condition by setting the magnetic field value H2, which is the sweep start value Hs, to a value X percent smaller than the maximum magnetizing force Hmax under no-load conditions. Therefore, a strong external magnetic field is not applied to the measurement sample S during the magnetic field sweep, and it is possible to accurately measure the deterioration of the magnetic properties when an external load is applied to the measurement sample S. Furthermore, since the magnetic properties of the first quadrant under a load condition can also be obtained, highly accurate demagnetizing field correction is possible, making it possible to accurately estimate the deterioration of the magnetic properties of the magnetic material installed in the motor device. In the second embodiment, when obtaining the magnetic properties under a load condition that return to the first quadrant via the third quadrant through the fourth quadrant, it is sufficient to set H = H2 as the sweep end value He.

[0067] Embodiment 3. A vibrating sample magnetometer according to embodiment 3 will be described with reference to FIGS. 10 and 11. FIG. 10 is a process diagram illustrating an example of the measurement procedure for the vibrating sample magnetometer according to embodiment 3. FIG. 11 is a diagram illustrating the magnetic characteristics (B-H loop) obtained under the second measurement condition (P1, T0) in a loaded state in embodiment 3. In embodiment 3, the magnetic characteristics of the measurement sample S under a loaded state are acquired using a first-order reversal curve (FORC) analysis technique. In the FORC measurement, when the magnetic field is swept in the negative direction from a positive saturation state to measure the magnetization curve, the magnetic field sweep direction is reversed at a magnetic field value Hr during demagnetization, and the magnetic field H is swept again toward positive saturation. By repeating this process while gradually changing the magnetic field value Hr, the inside of the astigmatism curve is filled with FORC. In the FORC analysis, information regarding the magnetization process within the bulk of the measurement sample is visualized.

[0068] First, as described with reference to FIG. 5 , the control device 10 sets the measurement conditions for the measurement sample S in the initial state to the first measurement conditions (P0, T0) under the no-load condition described above. P0 = 0 MPa, and T0 = 25°C. The control device 10 also controls the exciting electromagnet 5a to perform full-loop magnetic field sweep control, applying an external magnetic field H to the measurement sample S. That is, the external magnetic field is swept from H = 0 to the positive limit value Hlmt, from the positive limit value Hlmt to the negative limit value −Hlmt, and from the negative limit value −Hlmt to the positive limit value Hlmt. This magnetic field sweep control under the first measurement conditions (P0, T0) allows a full-loop B-H loop, such as that shown in FIG. 5 , to be acquired (step S300).

[0069] Next, the control device 10 applies an external magnetic field H to the measurement sample S from H=0 to the positive limit value Hlmt of the measurement device while keeping the measurement conditions of the measurement sample S set to the first measurement conditions (P0, T0) in an unloaded state.

[0070] Next, the control device 10 reduces the external magnetic field H to a magnetic field value H2, as in the second embodiment. H2<Hmax. Furthermore, the control device 10 sets the measurement conditions of the measurement sample S to second measurement conditions (P1, T0) under a load. For example, the pressure P1 is set to 100 MPa and the temperature T0 is set to 25°C. After the temperature and pressure of the measurement sample S have stabilized, the control device 10 sweeps the magnetic field in the negative direction from the magnetic field value H2 to the magnetic field value Hr under this load. Then, at the magnetic field value Hr, the control device 10 reverses the magnetic field sweep direction and sweeps the magnetic field in the positive direction from the magnetic field value Hr to the magnetic field value H2 (step S310). This results in a magnetization curve such as that shown by line J1 in FIG. 11. Furthermore, by repeatedly executing this process while gradually changing the magnetic field value Hr, the inside of the asteresis loop is filled with FORC, as shown in FIG. 11 (steps S320 and S330).

[0071] Next, the control device 10 calculates the difference ΔB4 between the magnetic properties under the first measurement condition (P0, T0) and the magnetic properties under the second measurement condition (P1, T0) (step S340). This difference ΔB4 makes it possible to grasp the demagnetization characteristics when stress is applied to the measurement sample S.

[0072] As described above, in the third embodiment, the magnetic field value H2, which is the sweep start value Hs, is set to a value smaller than the maximum magnetizing force Hmax in the no-load state, and the magnetic field sweep control in the loaded state is performed using the FORC analysis method. This makes it possible to measure the deterioration state of the magnetic properties more accurately when an external load is applied to the measurement sample S. Furthermore, since the magnetic properties in the first quadrant in the loaded state can also be obtained, highly accurate demagnetizing field correction is possible, and it becomes possible to accurately estimate the deterioration state of the magnetic properties of the magnetic material installed in the motor device. Note that in the third embodiment, the first magnetic field value Ha obtained in the first embodiment may be used as the sweep start value Hs.

[0073] In the fourth embodiment, the temperature T of the measurement sample S when acquiring the magnetic properties under a load is set to a temperature T1, which is different from the temperature T (= T0) of the measurement sample S when acquiring the magnetic properties under no load. By doing so, it becomes possible to grasp irreversible demagnetization due to temperature changes in addition to pressure changes.

[0074] Specifically, the second measurement conditions for the loaded state in step S110 of the process diagram of FIG. 4 are set to (P1, T1), for example. For example, the pressure P1 is set to 100 MPa, and the temperature T1 is set to 150° C. Other measurement conditions, such as the external magnetic field H, are the same as those described for step S110. Furthermore, in step S160 of FIG. 4, when acquiring the magnetic properties of the measurement sample S under a loaded state, the temperature T of the measurement sample S may be set to a value different from the temperature T of the measurement sample S when acquiring the magnetic properties under no load. Similarly, in the second and third embodiments, when acquiring the magnetic properties under a loaded state (step S210 of FIG. 8, step S310 of FIG. 10), the temperature T of the measurement sample S may be set to a value different from the temperature T of the measurement sample S when acquiring the magnetic properties under no load.

[0075] As described above, according to the fourth embodiment, it is possible to accurately measure the deterioration state of the magnetic properties when an external load and a temperature change are applied to the measurement sample S.

[0076] The configurations shown in the above embodiments are examples of the contents of the present disclosure, and may be combined with other known technologies, and parts of the configurations may be omitted or modified within the scope of the gist of the present disclosure.

[0077] 1 sample-accommodating vibrating body, 1a sample storage section, 1b pressure application rod, 1c temperature detection section, 2 support stand, 3 vibration device, 4 external force application mechanism, 4a pressure detection section, 5 magnetic property imparting measurement section, 5a excitation electromagnet, 5b detection coil, 7 temperature control gas supply pipe, 8 temperature control gas supply device, 10 control device, 11 main control section, 12 magnetic property acquisition section, 13 temperature acquisition section, 14 pressure acquisition section, 15 vibration control section, 16 temperature control section, 17 pressure control section, 18 external load environment determination section, 19 external magnetic field sweep section, 100 vibrating sample magnetometer, 101 processor, 102 memory, 103 interface circuit.

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