WO2022127080A1 - 一种磁矩的测量装置及方法 - Google Patents

一种磁矩的测量装置及方法 Download PDF

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WO2022127080A1
WO2022127080A1 PCT/CN2021/104323 CN2021104323W WO2022127080A1 WO 2022127080 A1 WO2022127080 A1 WO 2022127080A1 CN 2021104323 W CN2021104323 W CN 2021104323W WO 2022127080 A1 WO2022127080 A1 WO 2022127080A1
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magnetic
magnetic field
sample
rubidium
coil
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PCT/CN2021/104323
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English (en)
French (fr)
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缪培贤
冯浩
涂建辉
廉吉庆
王剑祥
张金海
崔敬忠
刘志栋
杨世宇
刘宗鑫
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兰州空间技术物理研究所
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Publication of WO2022127080A1 publication Critical patent/WO2022127080A1/zh

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/12—Measuring magnetic properties of articles or specimens of solids or fluids
    • G01R33/1215—Measuring magnetisation; Particular magnetometers therefor

Definitions

  • the invention relates to the technical field of magnetic field measurement, in particular to a magnetic moment measurement device and method based on a pump-detection type rubidium atomic magnetometer.
  • the commonly used precision magnetometers for measuring magnetic moment are Superconducting Quantum Interference Device (SQUID) magnetometer and Vibrating Sample Magnetometer (VSM).
  • SQUID Superconducting Quantum Interference Device
  • VSM Vibrating Sample Magnetometer
  • the detection coil When using the SQUID to measure the magnetic moment generated by the magnetic sample in the magnetic field, the magnetic flux in the detection coil changes through the up and down movement of the transmission system. According to the law of electromagnetic induction, the detection coil generates a magnetically induced electromotive force, which is proportional to the rate of change of the magnetic flux.
  • the signal measured by the SQUID is formed by amplification and coil coupling, and the magnetic moment of the sample can be obtained by digitally fitting the signal set of one cycle period (or the average of multiple cycles into one cycle period) using a specific formula.
  • VSM uses the sample to vibrate periodically up and down in the detection coil, so that the magnetic flux in the detection coil changes periodically, thereby generating a magnetically induced electromotive force, and the electromotive force signal is proportional to the magnetic moment.
  • the national standard GB/Z 26082-2010 specifies the DC magnetic susceptibility (magnetic moment) measurement method of nanomaterials.
  • the magnetometers for magnetic moment measurement are SQUID and VSM, and the magnet residual field should be less than 5Gs during specific measurement. In the principle of measuring the magnetic moment of SQUID and VSM, the movement of the magnetic sample needs to be controlled.
  • the magnetic sample causes the change of magnetic flux in the detection coil, which leads to the induction of electromotive force in the detection coil.
  • the magnetic moment of the sample is obtained in proportion to the induced electromotive force. value.
  • the above measurement process does not directly trace the magnetic moment generated by the magnetic sample to the quantum natural reference.
  • the measurement error of the magnetic moment of the sample is related to the design of the detection coil and the measurement accuracy of the induced electromotive force.
  • Soft magnetic materials are easy to be magnetized and easy to demagnetize, and their basic characteristics are small coercive force.
  • the measurement of magnetic properties of soft magnetic samples is a difficult problem in basic research.
  • the commonly used magnetic performance testing systems SQUID-VSM all use superconducting magnets to provide a magnetic field.
  • the superconducting magnet current is zero, the residual magnetic field can reach several tens of Gauss due to the frozen magnetic flux. Being able to measure can cause a lot of errors.
  • the present invention provides a device and method for measuring magnetic moment based on a pump-detection rubidium atomic magnetometer.
  • the Larmor precession effect is a quantum natural benchmark.
  • Using a pump-detection rubidium atomic magnetometer based on the Larmor precession effect to measure the magnetic field generated by the magnetic moment of the sample the magnetic moment of the sample can be directly traced to the quantum natural benchmark.
  • the accuracy of magnetic moment measurement of magnetic samples is significantly improved.
  • the magnetic moment measuring device of the present invention comprises: a pump-detection type rubidium atomic magnetometer, a background magnetic field generating assembly and a sample transfer rod;
  • the background magnetic field generating assembly includes a magnetic shielding cylinder and a background magnetic field coil placed inside the magnetic shielding cylinder; the magnetic shielding cylinder is used to realize geomagnetic shielding, and the background magnetic field coil is used to generate a background magnetic field in the magnetic shielding cylinder; the The background magnetic field is in the range of 200nT to 20000nT;
  • the pump-detection type rubidium atomic magnetometer is located in the magnetic shielding cylinder, the direction of the circularly polarized pumping light is parallel to the direction of the background magnetic field, and the direction of the linearly polarized detection light is perpendicular to the direction of the background magnetic field;
  • the pump-detection type rubidium atomic magnetometer It is used to measure the magnetic field of the spatial position of the rubidium bubble in the pump-detection type rubidium atomic magnetometer;
  • the pump-detection type rubidium atomic magnetometer measures the magnetic field in the closed-loop working state or the open-loop working state;
  • the sample transfer rod is used to send the sample to be tested into the magnetic shielding cylinder.
  • the connecting line between the sample to be tested and the rubidium bubble is parallel to the direction of the background magnetic field; the sample transfer rod is parallel to the line between the sample to be tested and the rubidium bubble. Move to linearly change the distance between the sample to be tested and the rubidium bubble.
  • the sample to be tested is a standard coil assembly;
  • the standard coil assembly includes a standard coil and a 6.5-bit precision current source; wherein, the standard coil is wound around one end of the sample transfer rod, and is located on the axis of the magnetic shielding cylinder, and is quasi-standard.
  • the axis of the coil is parallel to the direction of the background magnetic field; the output end of the 6.5-bit precision current source is connected to the standard coil.
  • the standard coil generates different magnetic moments to be measured by changing the output current of the 6.5-bit precision current source.
  • the sample to be tested is a magnetic sample.
  • the distance between the sample to be tested and the rubidium bubble is increased by manual method, or by using an electronically controlled displacement stage to slowly move linearly or stepwise.
  • the magnetic shielding cylinder is cylindrical, with a diameter of ⁇ 500mm and a length greater than or equal to 700mm; or, the magnetic shielding cylinder is replaced with a magnetic shielding room with a magnetic shielding coefficient better than 10 ⁇ 3 .
  • it also includes a non-magnetic constant temperature system, which is used to keep the temperature of the sample to be tested constant.
  • the present invention also provides a method for measuring magnetic moment, which adopts the above-mentioned measuring device to measure, including the following steps:
  • Step 1 Start the pumping-detection type rubidium atomic magnetometer, and adjust the current flowing into the background magnetic field coil according to the magnetic field value measured by the pumping-detection type atomic magnetometer, so that the background magnetic field is in the range of 200nT ⁇ 20000nT; set Determine the distance between the sample to be tested and the rubidium bubble;
  • Step 2 The sample transfer rod is used to send the sample to be tested into the magnetic shielding cylinder;
  • Step 3 Set the pumping-detection type rubidium atomic magnetometer to work, move the sample transfer rod, and use the pumping-detection type rubidium atomic magnetometer to measure the magnetic field at the spatial position of the rubidium bubble during the moving process.
  • the magnetic field value is the algebraic sum of the magnetic field generated by the background magnetic field and the magnetic moment of the sample to be measured at the spatial position of the rubidium bubble;
  • Step 4 Subtract the background magnetic field value from the measured value of the pump-detection rubidium atomic magnetometer in step 3 to obtain the process in which the distance between the sample to be tested and the rubidium bubble increases linearly from r 0 to (r 0 +x) , a series of magnetic field values B' generated by the magnetic moment of the sample to be tested at the spatial position of the rubidium bubble;
  • step 3 if the measured magnetic field value exceeds the range of the pump-detection rubidium atomic magnetometer during the measurement process, then return to step 1 to increase the distance between the sample to be tested and the rubidium bubble, and at the same time appropriately increase the distance. background magnetic field.
  • the magnetic moment to be measured can be directly traced to the quantum natural reference, which provides ideas for the quantum measurement of the magnetic moment.
  • the sample magnetic moment value is only related to
  • the fitting coefficient of the graph is related to k, where B' and (r 0 +x) are both traceable to the quantum natural datum: B' can be measured by a pump-detection rubidium atomic magnetometer based on the Larmor precession quantum natural datum, (r 0 +x) is traceable to the laser wavelength.
  • the magnetic moment of the current-carrying standard coil is proportional to the magnetic field generated at a fixed distance on the axis. Therefore, a current-carrying standard coil at a fixed position away from the rubidium bubble can be used to calibrate the magnetic moment of the magnetic sample at the same position, thus avoiding the motion of the magnetic sample.
  • Certain magnetic samples are sensitive to vibration or rotation, such as magnetic liquids, and the present invention has the ability to measure the magnetic moment of magnetic samples in situ.
  • FIG. 1 is a structural diagram of an apparatus for measuring the magnetic moment of a current-carrying standard coil according to the present invention.
  • 1-magnetic shielding cylinder 2-background magnetic field coil, 3-radio frequency magnetic field coil, 4-rubidium bubble heating module, 5-rubidium bubble, 11-standard coil, 9-6.5 position precision current source, 10-sample transmission rod.
  • FIG. 2 is a physical diagram (a) and a schematic size diagram (b) of the self-made standard coil 11 used in the present invention.
  • the standard coil 11 is made of copper wire with a diameter of 0.33mm, and the number of turns of the coil is 20.
  • the double-layered coil is tightly wound on a long glass tube with a diameter of 12mm.
  • the present invention approximately considers that the radius R of the standard coil 11 is 6.33 mm.
  • Figure 3 shows the magnetic field values measured and recorded by the pump-detection type rubidium atomic magnetometer during the process of passing current, moving position, and removing the current to the standard coil 11 at a distance of 20 cm from the rubidium bubble.
  • the background magnetic field is set to 500nT.
  • the standard coil 11 After the standard coil 11 is supplied with a 1A current, it moves 0cm, 1cm, 2cm, 3cm, 4cm, and 5cm successively. After each movement, it is measured for more than 10 seconds. Finally, the current-carrying standard coil is moved. 11. Pull out the magnetic shielding cylinder 1.
  • the pump-detection type rubidium atomic magnetometer adopts the open-loop mode to measure and record the magnetic field value with a magnetic field sampling rate of 10 Hz.
  • FIG. 4 is the result obtained after subtracting the background magnetic field and averaging the platform data from FIG. 3 .
  • FIG. 5 is the result of the transformation of the coordinate axes of FIG. 4 .
  • FIG. 6 shows the theoretical and experimental results of the magnetic moment generated by the current passing into the standard coil 11 and the current-carrying standard coil 11 .
  • FIG. 7 is a structural diagram of a device for measuring the magnetic moment of a soft magnetic sample according to the present invention.
  • 1-magnetic shielding cylinder 2-background magnetic field coil, 3-radio frequency magnetic field coil, 4-rubidium bubble heating module, 5-rubidium bubble, 6-sample chamber, 7-soft magnetic sample, 8-magnetization coil, 9 - 6.5 position precision current source, 10 - sample transfer rod.
  • Fig. 8 shows the magnetic moment generated by the remanence of the sample after the pulse saturation magnetization of the soft magnetic sample of the permalloy strip measured by the present invention.
  • Figure 8 the device for pulse saturation magnetization of the permalloy strip soft magnetic sample is referred to Figure 7, the permalloy strip soft magnetic sample is 11 cm away from the rubidium bubble, and the background magnetic field is set to 500 nT.
  • Figure (a) is the measurement result of the atomic magnetometer output when there is a sample in the magnetizing coil 8 with a +1A current magnetized for 30 seconds.
  • the invention provides a magnetic moment measurement device and method based on a pump-detection type rubidium atomic magnetometer.
  • the invention utilizes the pump-detection type rubidium atomic magnetometer to measure the absolute magnetic field with high sensitivity, and realizes the rapid measurement of the current-carrying standard coil (or magnetic sample) during the linear change of the distance between the current-carrying standard coil (or magnetic sample) and the rubidium bubble.
  • the magnetic moment generates the algebraic sum of the magnetic field and the background magnetic field at the position of the rubidium bubble. After deducting the background magnetic field from the measured magnetic field value, the magnetic moment of the current-carrying standard coil (or magnetic sample) is obtained through data analysis.
  • the device of the present invention for measuring the magnetic moment of a current-carrying standard coil using a pump-detection atomic magnetometer is shown in Figure 1, including: a pump-detection type rubidium atomic magnetometer, a background magnetic field generating component, and a standard coil component.
  • the composition and working principle of the pumping-detection type rubidium atomic magnetometer are shown in the authorized invention patent "A rubidium atomic magnetometer and its magnetic field measurement method" (patent number: 201710270545.8).
  • the pumping-detection method in Fig. 1 of the present invention only lists three components: the radio frequency magnetic field coil 3, the rubidium bubble heating module 4 and the rubidium bubble 5, which are placed in the magnetic shielding cylinder 1 of the background magnetic field generating assembly, and placed in the background magnetic field 2.
  • the uniform magnetic field area; the pump-detection rubidium atomic magnetometer has a range of 100nT to 100000nT, which is used to measure the algebraic sum of the magnetic field and the background magnetic field generated by the magnetic moment of the current-carrying standard coil 11 at the spatial position of the rubidium bubble 5; the present invention sets The value of the background magnetic field is in the range of 200nT to 20000nT.
  • the pump-detection rubidium atomic magnetometer can be in a closed-loop working state or an open-loop working state. In the specific measurement, the magnetic moment of the current-carrying standard coil 11 is in the rubidium bubble.
  • the algebraic sum of the magnetic field and the background magnetic field generated at the spatial position should be within the range of the pump-detection rubidium atomic magnetometer.
  • the background magnetic field is appropriately increased; the pump-detection rubidium atomic magnetometer of the present invention can be replaced by other quantum magnetometers measuring absolute magnetic fields, and the value range of the background magnetic field can be changed according to the range of other quantum magnetometers.
  • the background magnetic field generating assembly includes a magnetic shielding cylinder 1 and a background magnetic field coil 2.
  • the magnetic shielding cylinder 1 is mainly used for shielding the earth magnetic field.
  • An axially uniform and stable background magnetic field is generated in the cylinder 1.
  • the direction of the circularly polarized pumping light of the pump-detection rubidium atomic magnetometer is parallel to the direction of the background magnetic field, and the direction of the linearly polarized detection light is perpendicular to the direction of the background magnetic field.
  • the internal size of the magnetic shielding cylinder 1 can be selected to be larger than the size of ⁇ 500mm ⁇ 700mm in the embodiment of the present invention, or replaced with a magnetic shielding room with a magnetic shielding coefficient better than 10 ⁇ 3 , a large-sized magnetic shielding cylinder 1 or a magnetic shielding
  • the chamber can significantly reduce the influence of the magnetic moment of the current-carrying standard coil 11 to be measured on the magnetization state of the magnetic shielding cylinder 1, ensure the stability of the background magnetic field, and increase the adjustable range of the distance between the standard coil 11 and the rubidium bubble 5, which is conducive to expanding the magnetic moment Measuring range;
  • the background magnetic field coil 2 matched with the magnetic shielding cylinder 1 can generate a uniform background magnetic field at the spatial position of the rubidium bubble 5, and the magnetic field gradient is less than 1%, so as to ensure the best work of the pump-detection atomic magnetometer Conditions;
  • the background magnetic field measured and calibrated by the pumping detection type atomic magnetometer is in the range of
  • the standard coil assembly includes a standard coil 11, a 6.5-bit precision current source 9 and a sample transfer rod 10; wherein, the output end of the 6.5-bit precision current source 9 is connected to the standard coil 11, and the standard coil 11 is connected by changing the output current of the 6.5-bit precision current source 9.
  • the coil 11 generates different magnetic moments to be measured, and the sample transfer rod 10 is used to linearly change the distance between the standard coil 11 and the rubidium bubble 5; the direction of the sample transfer rod 10 moving the standard coil 11 (or the magnetic sample) is parallel or antiparallel to this The direction of the bottom magnetic field; the connecting line between the standard coil 11 (or the magnetic sample) and the center of the rubidium bubble 5 is parallel to the direction of the background magnetic field; the axis of the standard coil 11 is parallel to the direction of the background magnetic field.
  • the magnetic field generated by the current-carrying standard coil 11 on its axis is: where r 0 is the position on the axis of the standard coil 11 from the center of the circle, B' is the magnetic field generated by the current-carrying standard coil 11 at the position r 0 , and ⁇ 0 is the vacuum permeability;
  • the process of measuring the magnetic moment of the calibration current-carrying standard coil 11 is as follows: the sample transfer rod 10 linearly increases the distance (r 0 +x) between the current-carrying standard coil 11 and the rubidium bubble 5 , and the pump-detection atomic magnetometer measures and records In this process, the magnetic moment of the current-carrying standard coil 11 generates the algebraic sum of the magnetic field and the background magnetic field at the spatial position of the rubidium bubble 5 . A magnetic field B' is generated, according to Plot, the slope value k of the linear fit is equal to From this, the magnetic moment of the current-carrying standard coil 11 can be calculated
  • the magnetic moment of the current-carrying standard coil 11 is only The fitting coefficient of the graph is related to k, where B' and (r 0 +x) are both traceable to the quantum natural datum: B' can be measured by a pump-detection rubidium atomic magnetometer based on the Larmor precession quantum natural datum, (r 0 +x) is traceable to the laser wavelength. Therefore, the magnetic moment measurement method proposed in the present invention has the traceability property of quantum natural reference, and can improve the measurement accuracy and reproducibility.
  • the magnetic dipole layer and the current-carrying coil are equivalent, and the magnetic moment of the magnetic sample can be equivalent to the magnetic moment of the current-carrying coil, which is expressed by the expression It can be seen that when the distance between the current-carrying standard coil 11 or the magnetic sample and the rubidium bubble 5 is fixed, the magnetic field generated by the current-carrying standard coil 11 or the magnetic sample at the spatial position of the rubidium bubble 5 is proportional to their magnetic moment, so the distance from the rubidium bubble 5 can be fixed.
  • the current-carrying standard coil 11 at the position is used to calibrate the magnetic moment of the magnetic sample at the same position, and the method of moving the magnetic sample can also be used to directly measure and analyze the magnetic moment of the magnetic sample. For an irregular magnetic sample, the present invention measures the projected component of the sample's magnetic moment in the direction of the background magnetic field.
  • the device for measuring the magnetic moment of a soft magnetic sample using a pump-detection atomic magnetometer in the present invention is shown in Figure 7, including: a pump-detection type rubidium atomic magnetometer, a background magnetic field generating component, and a soft magnetic sample magnetization and demagnetization component .
  • the soft magnetic sample magnetization and demagnetization assembly is used to manipulate the magnetization state of the soft magnetic sample.
  • the soft magnetic sample 7 can be selected as a small-sized or trace sample suitable for a superconducting quantum interference device (Superconducting Quantum Interference Device, SQUID) magnetometer, and a country can also be selected.
  • SQUID superconducting Quantum Interference Device
  • the distance between them is determined by the geometric symmetry center of the soft magnetic sample 7 and the rubidium bubble 5.
  • an electronically controlled displacement stage can be used to increase the distance slowly and linearly The distance between the current-carrying standard coil 11 (or the magnetic sample) and the rubidium bubble 5, or use an electronically controlled displacement stage to increase the distance between the current-carrying standard coil 11 (or the magnetic sample) and the rubidium bubble 5 in a stepwise manner in the present invention.
  • the background magnetic field generated by the background magnetic field coil 2 can be selected.
  • the direction is regarded as the positive direction of the magnetic field of the test device, and correspondingly, the standard coil 11 in FIG. 1 and the direction of the magnetic field generated by the magnetizing coil 8 in FIG. 7 can be defined.
  • the background magnetic field coil 2, the standard coil 11, the sample chamber 6, the magnetizing coil 8 and the sample transfer rod 10 are all made of non-magnetic materials; in order to improve the reproduction of the magnetic moment measurement results of the soft magnetic sample 7 For stability and accuracy, it is preferable to keep the sample chamber 6 at a constant temperature.
  • the present invention carries out the method for magnetic moment measurement based on the above-mentioned measuring device as follows:
  • Step 1 Start the pump-detection type rubidium atomic magnetometer, and adjust the magnitude of the current flowing into the background magnetic field coil 2 through the output magnetic field value of the pump-detection type atomic magnetometer to set the background magnetic field size, so that the background magnetic field is set.
  • the set value is in the range of 200nT ⁇ 20000nT; set the distance between the standard coil 11 (or the soft magnetic sample 7) and the rubidium bubble 5;
  • Step 2 When the measurement object is the standard coil 11, use the 6.5-bit precision current source 9 to pass a specific current I to the standard coil 11, so that the standard coil 11 generates a magnetic moment, and the measurement device is shown in Figure 1; when the measurement object is a soft magnetic Sample 7, adopts the measuring device of FIG. 7 to pulse saturation magnetization of soft magnetic sample 7, and after the pulse current is turned off, the soft magnetic sample 7 produces a magnetic moment corresponding to saturation remanence;
  • Step 3 Set the pump-detection rubidium atomic magnetometer to be in working state, and use the sample transfer rod 10 to stepwise increase the distance between the current-carrying standard coil 11 (or the soft magnetic sample 7 ) and the rubidium bubble 5 with a specific step size , the residence time of each step should ensure that there are more than 20 magnetic field values on the magnetic field step measured by the pump-detection rubidium atomic magnetometer, and the average value of these magnetic field values is calculated, which represents the background magnetic field and the current-carrying standard coil.
  • Step 4 Subtract the background magnetic field value from the average magnetic field value calculated in step 3 to obtain the distance (r 0 +x) between the current-carrying standard coil 11 (or the soft magnetic sample 7 ) and the rubidium bubble 5 in the process of linear increase , a series of magnetic field values B' generated by the magnetic moment of the current-carrying standard coil 11 (or the soft magnetic sample 7) at the spatial position of the rubidium bubble 5;
  • the soft magnetic sample 7 can be replaced with other magnetic samples, and a non-magnetic constant temperature system can be designed for the magnetic sample.
  • the measurement temperature is set according to the experimental needs, and the temperature of the magnetic sample needs to be kept constant during the measurement process. .
  • the method for measuring magnetic moment based on the pump-detection type rubidium atomic magnetometer of the present invention will be specifically described below with reference to two embodiments.
  • the measurement object in the first embodiment is a current-carrying standard coil
  • the measurement object in the second embodiment is a soft magnetic sample with a permalloy strip. .
  • Fig. 1 shows the structure diagram of the device of the present invention for measuring the magnetic moment of the current-carrying standard coil
  • Fig. 2 shows the physical diagram (a) and the size diagram (b) of the self-made standard coil 11 used in the present invention.
  • the standard coil 11 is made of enameled copper wire with a diameter of 0.33mm, and the number of turns of the coil is 20, and the double-layer is tightly wound on a long glass tube with a diameter of 12mm.
  • the present invention approximately considers that the radius R of the standard coil 11 is 6.33 mm.
  • Step 1 Start the pump-detection type rubidium atomic magnetometer, set the working sequence of the pump-detection type rubidium atomic magnetometer, and the working cycle is 100ms, in which the pumping light duration is 30ms, the radio frequency field duration is 0.1ms,
  • the magnetometer is in continuous working state and completes 10 working cycles per second;
  • the magnitude of the background magnetic field is set by adjusting the magnitude of the current flowing into the background magnetic field coil 2 through the output magnetic field value of the pump-detection atomic magnetometer, so that the background
  • the set value of the magnetic field is 500nT;
  • the distance between the standard coil 11 and the rubidium bulb 5 is set to 20cm;
  • Step 3 Set the pumping-detection type rubidium atomic magnetometer in the working state, and use the sample transfer rod 10 to increase the distance between the current-carrying standard coil 11 and the rubidium bubble 5 in steps of 1 cm, and the dwell time of each step exceeds 10 seconds, take 100 magnetic field values on the step to calculate the average value, the average value represents the algebraic sum of the magnetic field generated by the background magnetic field and the magnetic moment of the current-carrying standard coil 11 at the spatial position of the rubidium bubble 5;
  • Figure 3 shows the standard coil 11 The magnetic field value measured and recorded by the pump-detection rubidium atomic magnetometer in the process of current, moving position and removing current;
  • Step 4 Subtract the background magnetic field value from the average magnetic field value calculated in step 3, to obtain the distance between the current-carrying standard coil 11 and the rubidium bubble 5 (r 0 +x) in the process of linearly increasing, the current-carrying standard coil 11 .
  • Figure 4 is the result obtained after subtracting the background magnetic field from Figure 3 and averaging the platform data;
  • the above steps realize the measurement of the magnetic moment of the current-carrying standard coil 11 . Further set the distance between the standard coil 11 and the rubidium bulb 5 to be 10cm, and the current passing through the standard coil to be 0.02A, 0.04A, 0.06A, 0.08A, and 0.1A, respectively, and to obtain the current-carrying standard coil 11 according to the above steps. value and theoretical value; set the distance between the standard coil 11 and the rubidium bubble 5 to be 20cm, and the current passing through the standard coil is 0.2A, 0.4A, 0.6A, 0.8A, 1.2A, respectively, and the current-carrying standard is obtained according to the above steps. Experimental and theoretical values of coil 11.
  • the measurement process in step 3 makes the distance between the standard coil 11 and the rubidium bubble 5 finally become 25cm, and at this time the current-carrying standard coil 11 and the magnetic shielding cylinder end cover If the distance is 10cm, the magnetic field generated by the current-carrying standard coil 11 will change the magnetization state of the end cover of the magnetic shielding cylinder 1, thereby changing the background magnetic field value, which will eventually lead to a large measurement error, so increase the axial dimension of the magnetic shielding cylinder 1. Post-measurement results will be better, or use a magnetically shielded room with a magnetic shielding factor better than 10 -3 .
  • the initial distance between the standard coil and the rubidium bulb in Table 1 is manually measured with a ruler with millimeter precision, which inevitably introduces manual measurement errors. Assuming that the manual measurement error is within 10mm, the standard coil and the rubidium bulb within the error range are used. The initial spacing value is re-fitted to the experimental data, and the relative error between the experimental value and the theoretical value is obtained by taking the current passing into the standard coil as 0.1A as an example. The specific values are shown in the following table.
  • the magnetic moment when the current passing through the standard coil in Table 1 is 0.02A to 0.1A
  • the relative error between the measured experimental value and the theoretical value is less than 1%.
  • the first embodiment shows that by reducing the measurement error of the initial distance between the standard coil and the rubidium bubble, the measurement accuracy of the magnetic moment of the current-carrying standard coil can be significantly improved.
  • the experimental idea is reversed, and the experiment of measuring the magnetic moment of the current-carrying standard coil can be analyzed.
  • the relative error between the value and the theoretical value can be used to calibrate the initial distance between the standard coil and the rubidium bubble. This experimental idea can be used for the in-situ measurement of the magnetic moment of the magnetic material sample.
  • Embodiment 2 is a diagrammatic representation of Embodiment 1:
  • FIG. 7 is a structural diagram of a device for measuring the magnetic moment of a soft magnetic sample according to the present invention.
  • the soft magnetic sample is a cylindrical sample with a diameter of less than 10mm and a length of 20mm, which is a cylindrical sample with a diameter of less than 10mm and a length of 20mm, which is made of a strip-shaped 1J85 permalloy strip with a width of 20mm, a length of 100mm and a thickness of 0.1mm. Symmetrical distribution.
  • Step 1 Start the pump-detection type rubidium atomic magnetometer, set the working sequence of the pump-detection type rubidium atomic magnetometer, and the working cycle is 100ms, in which the pumping light duration is 30ms, the radio frequency field duration is 0.1ms,
  • the magnetometer is in continuous working state and completes 10 working cycles per second;
  • the magnitude of the background magnetic field is set by adjusting the magnitude of the current flowing into the background magnetic field coil 2 through the output magnetic field value of the pump-detection atomic magnetometer, so that the background
  • the set value of the magnetic field is 500nT;
  • the distance between the soft magnetic sample 7 and the rubidium bubble 5 is set to 11cm;
  • Step 2 When there is a soft magnetic sample 7 in the magnetizing coil 8, the +1A current is magnetized for 30 seconds, and the magnetic moment to be measured after the saturation pulse magnetization of the soft magnetic sample 7 is obtained after removing the current;
  • Figure 8(a) shows the atomic magnetometer after removing the current.
  • the measured magnetic field value shows that the magnetic moment generated by the magnetic moment of the soft magnetic sample 7 at the spatial position of the rubidium bubble 5 decays slowly;
  • Step 3 Set the pumping-detection type rubidium atomic magnetometer to work, and use the sample transfer rod 10 to increase the distance between the soft magnetic sample 7 and the rubidium bubble 5 in steps with a step size of 5 mm, and the dwell time of each step exceeds 10 Second, take 20 magnetic field values on the step to calculate the average value, the average value represents the algebraic sum of the magnetic moment generated by the magnetic moment of the soft magnetic sample 7 at the spatial position of the rubidium bubble 5 and the background magnetic field;
  • Figure 8(b) shows the soft magnetic sample 7. The magnetic field value measured and recorded by the pump-detection rubidium atomic magnetometer during the process of moving the position and pulling out the magnetic shielding cylinder;
  • Step 4 Subtract the background magnetic field value from the average magnetic field value calculated in step 3 to obtain the magnetic moment of the soft magnetic sample 7 in the process of linearly increasing the distance (r 0 +x) between the soft magnetic sample 7 and the rubidium bubble 5 .
  • Figure 8(c) is the result obtained after subtracting the background magnetic field and averaging the platform data from Figure 8(b);
  • the magnetic moment m measured by the above steps after the saturation pulse magnetization of the soft magnetic sample is 3.91 ⁇ 10 ⁇ 4 A ⁇ m 2 .
  • the current-carrying standard coil 11 or the soft magnetic sample 7 changes the magnetization state of the magnetic shielding cylinder 1, thereby changing the background magnetic field and introducing The measurement error can be improved by using a large-sized magnetic shielding cylinder or a magnetic shielding room;
  • the sample transfer rod 10 increases the distance between the current-carrying standard coil 11 (or the soft magnetic sample 7 ) and the rubidium bubble 5 manually.
  • the magnetic moment measurement error mainly comes from the measurement error of the distance between the standard coil 11 (or soft magnetic sample 7 ) and the rubidium bubble 5 , which can be improved by using a high-precision electronically controlled displacement stage (or laser ranging).
  • Embodiment 1 and Embodiment 2 are only preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

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Abstract

一种磁矩的测量装置，其利用抽运‑检测型铷原子磁力仪高灵敏度地测量绝对磁场，实现了载流标准线圈（11）（或磁性样品）与铷泡（5）间距线性变化过程中快速测量出载流标准线圈（11）(或磁性样品)的磁矩在铷泡（5）位置产生磁场和本底磁场的代数和，测量磁场值扣除本底磁场后通过数据分析求得载流标准线圈（11）（或磁性样品）的磁矩。载流标准线圈（11）的磁矩与其在轴线上固定距离处产生的磁场成正比，可用距离铷泡（11）固定位置处的载流标准线圈（11）来定标相同位置磁性样品的磁矩，也可直接测量分析磁性样品的磁矩。一种磁矩测量方法。

Description

一种磁矩的测量装置及方法 技术领域
本发明涉及磁场测量技术领域，具体涉及一种基于抽运-检测型铷原子磁力仪的磁矩的测量装置及方法。
背景技术
在磁性材料测量领域，目前测量磁矩的常用精密磁强计是超导量子干涉器件(Superconducting Quantum Interference Device,SQUID)磁强计和振动样品磁强计(Vibrating Sample Magnetometer,VSM)。利用SQUID测量磁性样品在磁场中产生的磁矩时，通过传输系统的上下运动使探测线圈中的磁通量产生变化，根据电磁感应定律，探测线圈产生磁感应电动势，该电动势与磁通量变化率成比例，经放大及线圈耦合形成SQUID测得的信号，利用特定公式对一个循环周期(或多循环周期平均成一个循环周期)的信号集合进行数字拟合，即可获得样品的磁矩。VSM是利用样品在探测线圈内上下作周期性高频振动，使探测线圈中的磁通量产生周期性变化，从而生成磁感应电动势，该电动势信号与磁矩成比例。国家标准GB/Z 26082—2010规定了纳米材料直流磁化率(磁矩)测量方法，磁矩测量的磁强计即为SQUID和VSM，具体测量时磁体剩场需小于5Gs。SQUID和VSM测量磁矩的原理中都需控制磁性样品的运动，磁性样品在探测线圈中引起磁通量的变化，从而导致探测线圈感生出电动势，通过样品磁矩与感生电动势成比例得到样品磁矩值。上述测量过程没有直接将磁性样品产生的磁矩溯源到量子自然基准上，样品磁矩的测量误差与探测线圈的设计、感生电动势的测量准确度有关。
软磁材料容易磁化，也容易退磁，矫顽力小是其基本特征，软磁样品磁特 性测量是基础研究中的难点问题。目前常用的磁学性能测试系统(SQUID-VSM)都采用超导磁体来提供磁场，在超导磁体电流为零时，由于冻结磁通，剩余磁场可达几十高斯，这对软磁材料磁性能测量会造成很多错误。例如文献“于红云，超导磁体剩余磁场对软磁材料测试的影响[J].物理学报,2014,63(4):047502.”中指出，SQUID超导磁体退磁后剩余磁场有时大于30Gs，由此产生的磁场误差将导致测试的矫顽力、剩磁等数据不准确，甚至导致反向的磁滞回线，剩磁误差会引起特定磁场下软磁样品磁矩的测量误差。目前工业上采用抛移测量方法(软磁材料矫顽力的抛移测量方法.国家标准GB/T 3656-2008)或开磁路测量方法(在开磁路中测量磁性材料矫顽力的方法.国家标准GB/T 13888-2009.)来测量软磁材料的矫顽力，这两种方法无法进一步分析出软磁样品的磁矩信息。
发明内容
有鉴于此，本发明提供了一种基于抽运-检测型铷原子磁力仪测量磁矩的装置及方法。拉莫尔进动效应是一种量子自然基准，利用基于拉莫尔进动效应的抽运-检测型铷原子磁力仪测量样品磁矩产生的磁场，能够直接将样品磁矩溯源到量子自然基准上，显著提高磁性样品磁矩测量的准确度。
本发明的磁矩的测量装置，包括：抽运-检测型铷原子磁力仪、本底磁场产生组件和样品传送杆；
其中，本底磁场产生组件包括磁屏蔽筒和置于磁屏蔽筒内部的本底磁场线圈；磁屏蔽筒用于实现地磁屏蔽，本底磁场线圈用于在磁屏蔽筒中产生本底磁场；所述本底磁场在200nT至20000nT范围内；
抽运-检测型铷原子磁力仪位于磁屏蔽筒内，其圆偏振抽运光方向与本底磁场方向平行，线偏振探测光方向与本底磁场方向垂直；抽运-检测型铷原子磁力仪用于测量抽运-检测型铷原子磁力仪内铷泡空间位置的磁场；抽运-检测型铷原 子磁力仪在闭环工作状态或开环工作状态测量磁场；
样品传送杆用于将待测样品送至磁屏蔽筒内，待测样品与铷泡之间的连线平行于本底磁场方向；样品传送杆沿待测样品与铷泡之间的连线平行移动，线性改变待测样品与铷泡之间的距离。
较优的，所述待测样品为标准线圈组件；标准线圈组件包括标准线圈和6.5位精密电流源；其中，标准线圈缠绕在样品传送杆的一端，并位于磁屏蔽筒的轴线上，且准线圈轴线平行于本底磁场方向；6.5位精密电流源输出端与标准线圈相连接。
较优的，通过改变6.5位精密电流源的输出电流使标准线圈产生不同的待测磁矩。
较优的，所述待测样品为磁性样品。
较优的，采用人工手动的方式，或者采用电控位移台以缓慢线性移动或台阶式增大待测样品与铷泡的间距。
较优的，所述磁屏蔽筒为圆柱形，直径为φ500mm，长度大于或等于700mm；或者，磁屏蔽筒替换为磁屏蔽系数优于10 -3的磁屏蔽室。
较优的，还包括无磁恒温系统，用于待测样品的温度保持恒定不变。
本发明还提供了一种磁矩的测量方法，采用上述测量装置进行测量，包括如下步骤：
步骤1、启动抽运-检测型铷原子磁力仪，根据抽运-检测型原子磁力仪测量的磁场值调节通入本底磁场线圈的电流大小，使本底磁场在200nT～20000nT范围内；设定待测样品与铷泡的间距；
步骤2、采用样品传送杆用于将待测样品送至磁屏蔽筒内；
步骤3、设定抽运-检测型铷原子磁力仪处于工作状态，移动样品传送杆，并在移动过程中，采用抽运-检测型铷原子磁力仪对铷泡空间位置的磁场进行测 量，该磁场值为本底磁场和待测样品的磁矩在铷泡空间位置产生磁场的代数和；
步骤4、用步骤3中抽运-检测型铷原子磁力仪测量值减去本底磁场值，得到待测样品与铷泡的间距由r 0线性增大到(r 0+x)的过程中，待测样品的磁矩在铷泡空间位置产生的一系列磁场值B’；
步骤5、将步骤4中获得的一系列磁场值按照
Figure PCTCN2021104323-appb-000001
作图，线性拟合后得斜率k，则待测样品的磁矩为m＝2π/μ 0k 3/2，其中，μ 0是真空磁导率。
较优的，所述步骤3中，若测量过程中出现测量磁场值超出抽运-检测型铷原子磁力仪的量程，则返回步骤1增大待测样品与铷泡的间距，同时适当增大本底磁场。
有益效果：
(1)采用本发明的测量装置及方法可直接将待测磁矩溯源到量子自然基准上，为磁矩的量子计量提供思路。样品磁矩值只与
Figure PCTCN2021104323-appb-000002
图的拟合系数k有关，其中B’和(r 0+x)都可溯源至量子自然基准：B’可由基于拉莫尔进动量子自然基准的抽运-检测型铷原子磁力仪测量，(r 0+x)可溯源至激光波长。
(2)根据本发明测量原理，载流标准线圈的磁矩与其在轴线上固定距离处产生的磁场成正比。因此，可用距离铷泡固定位置处的载流标准线圈来定标相同位置处磁性样品的磁矩，这样避免了磁性样品的运动。某些磁性样品对振动或旋转较敏感，例如磁性液体，本发明具备原位测量磁性样品磁矩的能力。
附图说明
图1为本发明测量载流标准线圈磁矩的装置结构图。
其中，1－磁屏蔽筒，2－本底磁场线圈，3－射频磁场线圈，4－铷泡加热模块，5－铷泡，11－标准线圈，9－6.5位精密电流源，10－样品传送杆。
图2为本发明使用的自制标准线圈11实物图(a)和尺寸示意图(b)。
图2中，标准线圈11由直径为0.33mm的铜丝绕制而成，线圈匝数为20匝，双层紧密地绕制在直径为12mm的长玻璃管上。本发明近似认为标准线圈11的半径R为6.33mm。
图3为距离铷泡20cm处的标准线圈11通电流、移动位置、撤去电流过程中抽运-检测型铷原子磁力仪测量并记录的磁场值。
图3中，本底磁场设定为500nT，标准线圈11通入1A电流后，先后移动0cm、1cm、2cm、3cm、4cm、5cm，每次移动后测量10秒以上，最后将载流标准线圈11抽出磁屏蔽筒1，上述过程中抽运-检测型铷原子磁力仪采用开环模式以10Hz磁场采样率测量并记录磁场值。
图4为对图3进行本底磁场扣除和平台数据平均后得到的结果。
将图3的本底磁场扣除，并在每个平台上取一段稳定磁场数据求平均值；以载流标准线圈11与铷泡5间距(r 0+x)为横坐标，以载流标准线圈11的磁矩在铷泡5空间位置产生的磁场为纵坐标作图。
图5为图4坐标轴变换后的结果。
将图4中横坐标B’变换为(1/B’) 2/3，纵坐标(r 0+x)变换为(r 0+x) 2，线性拟合得斜率k为1.38446×10 6。
图6为通入标准线圈11的电流与载流标准线圈11产生磁矩的理论和实验结果。
图6中，理论结果由表达式m＝IπR 2＝(ni)πR 2计算得到，其中m是磁矩，I是总电流，n是线圈匝数，i是6.5位精密电流源设定的电流，R是标准线圈11的半径；实验结果由表达式
Figure PCTCN2021104323-appb-000003
求得，k是按照图3、图4、图5步骤获得的线性拟合系数，电流i≤0.1A时载流标准线圈11与铷泡5的初始间距为10cm， 电流i≥0.2A时载流标准线圈11与铷泡5的初始间距为20cm。
图7为本发明测量软磁样品磁矩的装置结构图。
其中，1－磁屏蔽筒，2－本底磁场线圈，3－射频磁场线圈，4－铷泡加热模块，5－铷泡，6－样品室，7－软磁样品，8－磁化线圈，9－6.5位精密电流源，10－样品传送杆。
图8为利用本发明测量坡莫合金带软磁样品脉冲饱和磁化后样品剩磁产生的磁矩。
图8中，坡莫合金带软磁样品脉冲饱和磁化的装置参考图7，坡莫合金带软磁样品距离铷泡11cm，本底磁场设为500nT。图(a)是磁化线圈8内有样品时+1A电流磁化30秒后原子磁力仪输出的测量结果，可见软磁样品7的剩磁在铷泡5空间位置产生的磁场衰减缓慢，1分钟内该磁场衰减不超过2％，表明坡莫合金带软磁样品剩磁状态能够很好地保持；图(b)是磁化线圈8中通入+1A电流，软磁样品7被磁化30秒后撤去电流，以5mm步长远离铷泡时抽运-检测型原子磁力仪测量并记录的磁场值；图(c)为对图(b)进行本底磁场扣除和平台数据平均后得到的结果，以软磁样品7与铷泡5间距(r 0+x)为横坐标，以软磁样品7的磁矩在铷泡5空间位置产生的磁场B’为纵坐标作图；图(d)是对图(c)坐标轴变换后的结果，线性拟合得系数为5.46701×10 6。
具体实施方式
下面结合附图并举实施例，对本发明进行详细描述。
本发明提供了一种基于抽运-检测型铷原子磁力仪的磁矩的测量装置及方法。本发明利用抽运-检测型铷原子磁力仪高灵敏度地测量绝对磁场，实现了载流标准线圈(或磁性样品)与铷泡间距线性变化过程中快速测量出载流标准线圈(或磁性样品)磁矩在铷泡位置产生磁场和本底磁场的代数和，测量磁场值扣除本 底磁场后通过数据分析求得载流标准线圈(或磁性样品)的磁矩。
本发明采用抽运-检测型原子磁力仪测量载流标准线圈磁矩的装置如图1所示，包括：抽运-检测型铷原子磁力仪、本底磁场产生组件、标准线圈组件。
抽运-检测型铷原子磁力仪的组成及工作原理见已授权的发明专利“一种铷原子磁力仪及其磁场测量方法”(专利号为：201710270545.8)，本发明图1中抽运-检测型铷原子磁力仪仅列出了射频磁场线圈3、铷泡加热模块4和铷泡5三个组件，它们被放置在本底磁场产生组件的磁屏蔽筒1中，置于本底磁场2的磁场均匀区；抽运-检测型铷原子磁力仪量程为100nT～100000nT，用于测量载流标准线圈11的磁矩在铷泡5空间位置产生磁场和本底磁场的代数和；本发明设定本底磁场取值在200nT至20000nT范围内，抽运-检测型铷原子磁力仪可处于闭环工作状态，也可处于开环工作状态，具体测量中，载流标准线圈11的磁矩在铷泡5空间位置产生磁场和本底磁场的代数和应在抽运-检测型铷原子磁力仪量程范围内，超出量程时(例如≤100nT)需增大载流标准线圈11和铷泡5的间距，同时适当增大本底磁场；本发明抽运-检测型铷原子磁力仪可被其他测量绝对磁场的量子磁力仪所替代，根据其他量子磁力仪的量程范围改变本底磁场的取值范围。
本底磁场产生组件包括磁屏蔽筒1和本底磁场线圈2，磁屏蔽筒1主要用于屏蔽地磁场，本底磁场线圈2轴对称地置于磁屏蔽筒1的内部，用于在磁屏蔽筒1内产生轴向均匀稳定的本底磁场，抽运-检测型铷原子磁力仪的圆偏振抽运光的方向与本底磁场方向平行，线偏振探测光的方向与本底磁场方向垂直。其中，优选地，磁屏蔽筒1内部尺寸可选择大于本发明实施例中φ500mm×700mm的尺寸，或者替换为磁屏蔽系数优于10 -3的磁屏蔽室，大尺寸磁屏蔽筒1或磁屏蔽室能够显著降低待测载流标准线圈11磁矩对磁屏蔽筒1磁化状态的影响，保证本底磁场的稳定，同时增加标准线圈11与铷泡5间距的可调整范围，有利 于扩大磁矩测量的量程；与磁屏蔽筒1配套的本底磁场线圈2能够在铷泡5空间位置产生均匀的本底磁场，磁场梯度小于1％，以保证抽运-检测型原子磁力仪的最佳工作条件；由抽运检测型原子磁力仪测量标定的本底磁场取值在200nT～20000nT范围内。
标准线圈组件包括标准线圈11、6.5位精密电流源9和样品传送杆10；其中，6.5位精密电流源9输出端与标准线圈11相连接，通过改变6.5位精密电流源9的输出电流使标准线圈11产生不同的待测磁矩，样品传送杆10用于线性地改变标准线圈11与铷泡5的间距；样品传送杆10移动标准线圈11(或磁性样品)的方向平行或反平行于本底磁场方向；标准线圈11(或磁性样品)与铷泡5中心之间的连线平行于本底磁场方向；标准线圈11轴线平行于本底磁场方向。
载流标准线圈11产生的磁矩为：m＝IπR 2，其中m是磁矩，I是电流，R是标准线圈11的半径；
载流标准线圈11在其轴线上产生的磁场为：
Figure PCTCN2021104323-appb-000004
其中r 0是标准线圈11轴线上距离圆心的位置，B’是r 0位置处载流标准线圈11产生的磁场，μ 0是真空磁导率；
沿着轴线使r 0增大x，上一表达式变形后得：
Figure PCTCN2021104323-appb-000005
测量标定载流标准线圈11的磁矩过程如下：样品传送杆10线性地增大载流标准线圈11与铷泡5的间距(r 0+x)，抽运-检测型原子磁力仪测量并记录该过程中载流标准线圈11的磁矩在铷泡5空间位置产生磁场和本底磁场的代数和，测量磁场值扣除本底磁场后得载流标准线圈11的磁矩在铷泡5空间位置产生磁 场B’，按照
Figure PCTCN2021104323-appb-000006
作图，线性拟合的斜率值k等于
Figure PCTCN2021104323-appb-000007
由此可计算出载流标准线圈11的磁矩
Figure PCTCN2021104323-appb-000008
在上述理论分析中，载流标准线圈11的磁矩只与
Figure PCTCN2021104323-appb-000009
图的拟合系数k有关，其中B’和(r 0+x)都可溯源至量子自然基准：B’可由基于拉莫尔进动量子自然基准的抽运-检测型铷原子磁力仪测量，(r 0+x)可溯源至激光波长。因此，本发明提出的磁矩测量方法具有量子自然基准的溯源属性，能够提高测量的准确度和复现性。
电磁学中磁偶极层与载流线圈具有等价性，磁性样品的磁矩可等效为载流线圈的磁矩，由表达式
Figure PCTCN2021104323-appb-000010
可知，当载流标准线圈11或磁性样品与铷泡5间距固定时，载流标准线圈11或磁性样品在铷泡5空间位置产生的磁场正比于它们的磁矩，因此可用距离铷泡5固定位置处的载流标准线圈11来定标相同位置处磁性样品的磁矩，也可采用移动磁性样品的方法直接测量并分析出磁性样品的磁矩。对于不规则的磁性样品，本发明测得该样品磁矩在本底磁场方向上的投影分量。
本发明采用抽运-检测型原子磁力仪测量软磁样品磁矩的装置如图7所示，包括：抽运-检测型铷原子磁力仪、本底磁场产生组件和软磁样品磁化和退磁组件。其中，软磁样品磁化和退磁组件用于操控软磁样品的磁化状态。当选用大尺寸磁屏蔽筒1或采用磁屏蔽室时，软磁样品7可选择适用于超导量子干涉器件(Superconducting Quantum Interference Device,SQUID)磁强计的小尺寸或微量样品，也可选择国家标准GB/T 3656-2008(软磁材料矫顽力的抛移测量方法)中描述的大尺寸样品，以软磁样品7和铷泡5的几何对称中心确定它们之间的 间距。
本发明实施例中样品传送杆10增大载流标准线圈11(或软磁样品7)与铷泡5的间距时采用人工手动的方式；优选地，可采用电控位移台缓慢线性地增大载流标准线圈11(或磁性样品)与铷泡5的间距，或采用电控位移台以本发明中台阶式增大载流标准线圈11(或磁性样品)与铷泡5的间距。
为分析图1中载流标准线圈11的磁矩方向，以及图7中软磁样品7的磁化状态，一般需对测量装置的磁场方向进行约定，一般可选本底磁场线圈2产生的本底磁场方向作为测试装置磁场的正方向，相应地可定义图1中标准线圈11，以及图7中磁化线圈8产生磁场的方向。
其中，图1和图7中本底磁场线圈2、标准线圈11、样品室6、磁化线圈8和样品传送杆10都由非磁性材料制成；为提高软磁样品7磁矩测量结果的再现性和准确性，较优的做法是让样品室6保持恒定温度。
本发明基于上述测量装置进行磁矩测量的方法如下：
步骤1、启动抽运-检测型铷原子磁力仪，通过抽运-检测型原子磁力仪输出的磁场值调节通入本底磁场线圈2的电流大小来设定本底磁场大小，使本底磁场设定值在200nT～20000nT范围内；设定标准线圈11(或软磁样品7)与铷泡5的间距；
步骤2、当测量对象为标准线圈11，利用6.5位精密电流源9向标准线圈11通入特定电流I，使标准线圈11产生磁矩，测量装置如图1所示；当测量对象为软磁样品7，采用图7的测量装置脉冲饱和磁化软磁样品7，脉冲电流关闭后使软磁样品7产生饱和剩磁对应的磁矩；
步骤3、设定抽运-检测型铷原子磁力仪处于工作状态，以特定步长利用样品传送杆10台阶式地增大载流标准线圈11(或软磁样品7)与铷泡5的间距，每个台阶停留时间应保证抽运-检测型铷原子磁力仪测量的磁场台阶上有超过 20个磁场值，计算出这些磁场值的平均值，该平均值代表本底磁场和载流标准线圈11(或软磁样品7)的磁矩在铷泡5空间位置产生磁场的代数和；上述测量过程中出现测量磁场值超出抽运检测型铷原子磁力仪的量程情况时(例如≤100nT)，返回步骤1增大载流标准线圈11(或软磁样品7)与铷泡5的间距，同时适当增大本底磁场；
步骤4、用步骤3中计算的平均磁场值减去本底磁场值，得到载流标准线圈11(或软磁样品7)与铷泡5的间距(r 0+x)在线性增加的过程中，载流标准线圈11(或软磁样品7)的磁矩在铷泡5空间位置产生的一系列磁场值B’；
步骤5、将步骤4中获得的一系列磁场值按照
Figure PCTCN2021104323-appb-000011
作图，线性拟合后得斜率k，计算出载流标准线圈11(或软磁样品7)的磁矩m＝2π/μ 0k 3/2。
上述步骤1～步骤5中，软磁样品7可被替换为其他磁性样品，可为磁性样品设计无磁恒温系统，根据实验需要设定测量温度，测量过程中磁性样品的温度需保持恒定不变。
下面结合两个实施例具体说明本发明基于抽运-检测型铷原子磁力仪测量磁矩的方法，实施例一测量对象为载流标准线圈，实施例二测量对象为坡莫合金带软磁样品。
实施例一：
图1显示了本发明测量载流标准线圈磁矩的装置结构图，图2显示了本发明使用的自制标准线圈11实物图(a)和尺寸示意图(b)。标准线圈11由直径为0.33mm的漆包铜丝绕制而成，线圈匝数为20匝，双层紧密地绕制在直径为12mm的长玻璃管上。本发明近似认为标准线圈11的半径R为6.33mm。
步骤1、启动抽运-检测型铷原子磁力仪，设置抽运-检测型铷原子磁力仪工作时序，工作周期为100ms，其中抽运光作用时长为30ms，射频场作用时长为 0.1ms，原子磁力仪处于连续工作状态，每秒完成10个工作周期；通过抽运-检测型原子磁力仪输出的磁场值调节通入本底磁场线圈2的电流大小来设定本底磁场大小，使本底磁场设定值在500nT；设定标准线圈11与铷泡5的间距为20cm；
步骤2、利用6.5位精密电流源9向标准线圈11通入1A电流，即20匝的标准线圈通入的总电流为20A，使标准线圈11产生磁矩；由表达式m＝IπR 2求得载流线圈产生磁矩为2.518×10 -3A·m 2；
步骤3、设定抽运-检测型铷原子磁力仪处于工作状态，以1cm步长利用样品传送杆10台阶式地增大载流标准线圈11与铷泡5的间距，每个台阶停留时间超过10秒，取台阶上100个磁场值计算平均值，该平均值代表本底磁场和载流标准线圈11的磁矩在铷泡5空间位置产生磁场的代数和；图3显示了标准线圈11通电流、移动位置、撤去电流过程中抽运-检测型铷原子磁力仪测量并记录的磁场值；
步骤4、用步骤3中计算的平均磁场值减去本底磁场值，得载流标准线圈11与铷泡5的间距(r 0+x)在线性增加的过程中，载流标准线圈11的磁矩在铷泡5空间位置产生的一系列磁场值B’；图4是对图3进行本底磁场扣除和平台数据平均后得到的结果；
步骤5、将步骤4中获得的一系列磁场值按照
Figure PCTCN2021104323-appb-000012
作图，线性拟合后得斜率k＝1.38446×10 6，计算出载流标准线圈11的磁矩m＝2π/μ 0k 3/2＝3.069×10 -3A·m 2，该实验值与步骤2中理论值的相对误差为21.92％。
以上步骤实现了载流标准线圈11的磁矩的测量。进一步设定标准线圈11与铷泡5间距为10cm，标准线圈中通入电流分别为0.02A、0.04A、0.06A、0.08A、0.1A，按照上述步骤分别求得载流标准线圈11的实验值和理论值；设 定标准线圈11与铷泡5间距为20cm，标准线圈中通入电流分别为0.2A、0.4A、0.6A、0.8A、1.2A，按照上述步骤分别求得载流标准线圈11的实验值和理论值。上述理论值和实验值显示在图6中，具体数值见下表，当标准线圈11与铷泡5间距为10cm时，实验值与理论值的相对误差在5％～6％范围内，当标准线圈11与铷泡5间距为20cm时，实验值与理论值的相对误差在21％～23％范围内；实施例一采用的磁屏蔽筒1内部尺寸为φ500mm×700mm，铷泡5处于屏蔽筒正中心，当载流标准线圈11与铷泡5间距为20cm时，步骤3的测量过程使标准线圈11与铷泡5间距最终变为25cm，此时载流标准线圈11与磁屏蔽筒端盖的距离为10cm，载流标准线圈11产生的磁场将改变磁屏蔽筒1端盖的磁化状态，进而改变本底磁场值，最终导致较大的测量误差，因此增大磁屏蔽筒1轴向尺寸后测量结果会更佳，或使用磁屏蔽系数优于10 -3的磁屏蔽室。
表1
Figure PCTCN2021104323-appb-000013
表1中标准线圈与铷泡的初始间距由人工利用毫米精度的直尺测量，不可避免地引入了人工测量误差，假设人工测量误差在10mm范围内，利用误差范围内的标准线圈与铷泡的初始间距值重新拟合实验数据，以通入标准线圈的电流为0.1A为例获得实验值与理论值的相对误差，具体数值见下表。因此，若将上表中标准线圈与铷泡的初始间距0.1m替换为0.096m(即认为间距测量误差 为-4mm)，表1中通入标准线圈的电流为0.02A至0.1A时磁矩测量的实验值与理论值的相对误差小于1％。实施例一表明，通过降低标准线圈与铷泡初始间距的测量误差，可显著提高载流标准线圈磁矩的测量精度，将该实验思想反过来，可通过分析载流标准线圈磁矩测量的实验值与理论值的相对误差来标定标准线圈与铷泡的初始间距，该实验思想可用于磁性材料样品磁矩的原位测量。
表2
标准线圈与铷泡的初始间距(m) 实验值与理论值的相对误差：(实验值-理论值)/理论值
0.090 -6.98％
0.091 -5.77％
0.092 -4.56％
0.093 -3.34％
0.094 -2.11％
0.095 -0.88％
0.096 0.36％
0.097 1.60％
0.098 2.85％
0.099 4.10％
0.100 5.36％
实施例二：
图7为本发明测量软磁样品磁矩的装置结构图。软磁样品为由宽20mm、长100mm、厚0.1mm的带状1J85坡莫合金带沿长边卷绕成直径小于10mm、长度为20mm的圆筒状样品，该样品在空间产生的磁场呈轴对称性分布。
步骤1、启动抽运-检测型铷原子磁力仪，设置抽运-检测型铷原子磁力仪工作时序，工作周期为100ms，其中抽运光作用时长为30ms，射频场作用时长为0.1ms，原子磁力仪处于连续工作状态，每秒完成10个工作周期；通过抽运-检测型原子磁力仪输出的磁场值调节通入本底磁场线圈2的电流大小来设定本底磁场大小，使本底磁场设定值在500nT；设定软磁样品7与铷泡5的间距为11cm；
步骤2、磁化线圈8内有软磁样品7时+1A电流磁化30秒，撤去电流后得到软磁样品7饱和脉冲磁化后的待测磁矩；图8(a)显示撤去电流后原子磁力仪测量的磁场值，软磁样品7的磁矩在铷泡5空间位置产生的磁场衰减缓慢；
步骤3、设定抽运-检测型铷原子磁力仪处于工作状态，以5mm步长利用样品传送杆10台阶式地增大软磁样品7与铷泡5的间距，每个台阶停留时间超过10秒，取台阶上20个磁场值计算平均值，该平均值代表软磁样品7的磁矩在铷泡5空间位置产生磁场和本底磁场的代数和；图8(b)显示了软磁样品7移动位置及抽出磁屏蔽筒过程中抽运-检测型铷原子磁力仪测量并记录的磁场值；
步骤4、用步骤3中计算的平均磁场值减去本底磁场值，得软磁样品7与铷泡5的间距(r 0+x)在线性增加的过程中，软磁样品7的磁矩在铷泡5空间位置产生的一系列磁场值B’；图8(c)是对图8(b)进行本底磁场扣除和平台数据平均后得到的结果；
步骤5、将步骤4中获得的一系列磁场值按照
Figure PCTCN2021104323-appb-000014
作图，线性拟合后得斜率k＝5.46701×10 6，计算出软磁样品7的磁矩m＝2π/μ 0k 3/2＝3.91×10 -4A·m 2。
实施例二中软磁样品饱和脉冲磁化后由上述步骤测量出的磁矩m为3.91×10 -4A·m 2。图8(c)中(r 0+x)＝11cm时，B’为50.4634nT，因此可粗略估计，软磁样品位置在该位置时，ΔB’＝1nT将对应磁矩变化Δm＝7.75×10 -6A·m 2；图8(c)中(r 0+x)＝20cm时，B’为9.6488nT，因此可粗略估计，软磁样品在该位置时，ΔB’＝1nT将对应磁矩变化Δm＝4.05×10 -5A·m 2。
本发明实施例一和实施例二中磁矩测量误差来源主要有两各方面，第一是载流标准线圈11或软磁样品7改变磁屏蔽筒1的磁化状态，进而改变本底磁场，引入测量误差，可采用大尺寸磁屏蔽筒或磁屏蔽室进行改进；第二是样品传送杆10增大载流标准线圈11(或软磁样品7)与铷泡5的间距时采用人工手动的 方式，磁矩测量误差主要来源于标准线圈11(或软磁样品7)与铷泡5间距的测量误差，可采用高精度电控位移台(或激光测距)进行改进。
综上所述，实施例一和实施例二仅为本发明的较佳实施例而已，并非用于限定本发明的保护范围。凡在本发明的精神和原则之内，所作的任何修改、等同替换、改进等，均应包含在本发明的保护范围之内。

Claims (9)

  1. 一种磁矩的测量装置，其特征在于，包括：抽运-检测型铷原子磁力仪、本底磁场产生组件和样品传送杆10；
    其中，本底磁场产生组件包括磁屏蔽筒1和置于磁屏蔽筒1内部的本底磁场线圈2；磁屏蔽筒1用于实现地磁屏蔽，本底磁场线圈2用于在磁屏蔽筒1中产生本底磁场；所述本底磁场在200nT至20000nT范围内；
    抽运-检测型铷原子磁力仪位于磁屏蔽筒1内，其圆偏振抽运光方向与本底磁场方向平行，线偏振探测光方向与本底磁场方向垂直；抽运-检测型铷原子磁力仪用于测量抽运-检测型铷原子磁力仪内铷泡5空间位置的磁场；抽运-检测型铷原子磁力仪在闭环工作状态或开环工作状态测量磁场；
    样品传送杆10用于将待测样品7送至磁屏蔽筒1内，待测样品7与铷泡5之间的连线平行于本底磁场方向；样品传送杆10沿待测样品7与铷泡5之间的连线平行移动，线性改变待测样品7与铷泡5之间的距离。
  2. 如权利要求1所述的磁矩的测量装置，其特征在于，所述待测样品7为标准线圈组件；标准线圈组件包括标准线圈11和6.5位精密电流源9；其中，标准线圈11缠绕在样品传送杆10的一端，并位于磁屏蔽筒1的轴线上，且准线圈11轴线平行于本底磁场方向；6.5位精密电流源9输出端与标准线圈11相连接。
  3. 如权利要求2所述的磁矩的测量装置，其特征在于，通过改变6.5位精密电流源9的输出电流使标准线圈11产生不同的待测磁矩。
  4. 如权利要求1所述的磁矩的测量装置，其特征在于，所述待测样品7为磁性样品。
  5. 如权利要求1所述的磁矩的测量装置，其特征在于，采用人工手动的方式，或者采用电控位移台以缓慢线性移动或台阶式增大待测样品7与铷泡5的 间距。
  6. 如权利要求1所述的磁矩的测量装置，其特征在于，所述磁屏蔽筒1为圆柱形，直径为φ500mm，长度大于或等于700mm；或者，磁屏蔽筒1替换为磁屏蔽系数优于10 -3的磁屏蔽室。
  7. 如权利要求1所述的磁矩的测量装置，其特征在于，还包括无磁恒温系统，用于待测样品7的温度保持恒定不变。
  8. 一种磁矩的测量方法，其特征在于，采用如权利要求1～7任意一项所述的测量装置进行测量，包括如下步骤：
    步骤1、启动抽运-检测型铷原子磁力仪，根据抽运-检测型原子磁力仪测量的磁场值调节通入本底磁场线圈2的电流大小，使本底磁场在200nT～20000nT范围内；设定待测样品与铷泡5的间距；
    步骤2、采用样品传送杆10用于将待测样品7送至磁屏蔽筒1内；
    步骤3、设定抽运-检测型铷原子磁力仪处于工作状态，移动样品传送杆10，并在移动过程中，采用抽运-检测型铷原子磁力仪对铷泡5空间位置的磁场进行测量，该磁场值为本底磁场和待测样品的磁矩在铷泡5空间位置产生磁场的代数和；
    步骤4、用步骤3中抽运-检测型铷原子磁力仪测量值减去本底磁场值，得到待测样品与铷泡5的间距由r 0线性增大到(r 0+x)的过程中，待测样品的磁矩在铷泡5空间位置产生的一系列磁场值B’；
    步骤5、将步骤4中获得的一系列磁场值按照
    Figure PCTCN2021104323-appb-100001
    作图，线性拟合后得斜率k，则待测样品的磁矩为m＝2π/μ 0k 3/2，其中，μ 0是真空磁导率。
  9. 如权利要求8所述的测量方法，其特征在于，所述步骤3中，若测量过程中出现测量磁场值超出抽运-检测型铷原子磁力仪的量程，则返回步骤1增大 待测样品与铷泡5的间距，同时适当增大本底磁场。
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