Abnormal Hall effect comprehensive experiment platform for measuring tiny signals
By using a magnetic field generation module, a signal acquisition and amplification module, and a LabVIEW signal processing system, the problems of high sensitivity and low cost in measuring anomalous Hall effect micro voltage signals were solved, realizing a high-precision experimental platform suitable for basic physics experimental teaching.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-16
- Publication Date
- 2026-03-10
AI Technical Summary
Existing technologies struggle to measure anomalous Hall effect micro voltage signals with high sensitivity and low cost. Lock-in amplifiers on the market are expensive and lack precision. The stability of AD630 analog devices is affected by temperature and voltage. FPGA development has high barriers to entry, and microcontroller computing resources are insufficient.
A magnetic field generation module, a signal acquisition and amplification module, and a LabVIEW-based signal processing and analysis system, including an electromagnet, an AD8421 instrumentation amplifier, an NI USB-6009 data acquisition card, and a digital quadrature lock-in amplification algorithm, are used to achieve highly sensitive measurement of small signals.
It reduces experimental costs, improves measurement accuracy, and achieves high-sensitivity measurement of the anomalous Hall effect at the μV level, making it suitable for basic physics experimental teaching.
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Figure CN121633602A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of weak signal detection, in particular to an anomalous Hall effect comprehensive experiment platform for measuring micro signals. BACKGROUND
[0002] Anomalous Hall effect (AHE) is a physical phenomenon that depends on the spontaneous magnetization of magnetic materials to generate a transverse Hall voltage, and the Hall voltage has a magnetic hysteresis loop relationship with the magnetic field. At present, there is no university in China to teach the content of anomalous Hall effect in the undergraduate stage of college physics experiment course. In addition, the existing college physics experiment related to magnetic thin film only studies the in-plane magnetic anisotropy, and has not explored the perpendicular magnetic anisotropy.
[0003] Because the anomalous Hall effect generated by the anomalous Hall effect experiment at room temperature is very small, it is necessary to use a phase-locked amplifier to amplify the small voltage signal of the anomalous Hall effect. The phase-locked amplifier on the market is generally expensive, such as STANFORD SRS series products, which are fully functional and expensive. A cheaper solution is to use an AD630 integrated chip, but the precision of AD630 cannot meet the demand: AD630 is mainly optimized for target frequencies above 1KHz, and the analog low-pass filter added after it is difficult to make the passband very narrow, which is generally above 10Hz, which does not meet the requirement of high frequency precision and low target frequency. As an analog device, the stability of AD630 is greatly affected by temperature and voltage, and it is difficult to modify parameters for further optimization, which is not convenient for testing and further calibration.
[0004] The method for building a digital phase-locked amplifier is as follows: FPGA (Field Programmable Gate Array) has good high-speed signal processing capability, but the development threshold is high, the real-time performance is poor, and the precision depends on complex floating-point quantization algorithm; although the single-chip microcomputer has a certain application basis in the teaching of colleges and universities, the operation resources are obviously insufficient, and additional hardware facilities are needed to improve the operation precision and speed, which cannot present a good experimental effect.
[0005] Therefore, there is an urgent need for an anomalous Hall effect experiment platform that can measure the uV-level anomalous Hall effect micro-voltage signal with high sensitivity and extremely low cost. SUMMARY
[0006] The purpose of the present application is to provide an anomalous Hall effect comprehensive experiment platform for measuring micro signals, which can improve the high sensitivity of the digital phase-locked amplifier integrated device for measuring the anomalous Hall effect micro-voltage signal and reduce the cost.
[0007] To achieve the above purpose, the present application provides the following solutions: The application provides an abnormal Hall effect comprehensive experiment platform for measuring a micro signal, comprising: a magnetic field generating module for generating a controllable magnetic field perpendicular to a surface of a sample to be measured; a signal acquisition and amplification module for acquiring a uV-level abnormal Hall voltage signal generated by the sample to be measured, amplifying and analog-digital converting the uV-level abnormal Hall voltage signal, and obtaining a digital signal; a LabVIEW-based signal processing and analysis system for: running a digital quadrature phase-locked amplification algorithm, processing the digital signal, and obtaining a final Hall voltage amplitude; and determining a magnetic induction intensity corresponding to the final Hall voltage amplitude according to the final Hall voltage amplitude and a pre-calibrated magnetic induction intensity-output voltage curve.
[0008] Optionally, the magnetic field generating module comprises an electromagnet and a direct-current stabilized power supply for powering the electromagnet; the electromagnet comprises a core and a coil wound on the core, and the core has an adjustable air gap.
[0009] Optionally, the core comprises a yoke and two movable column heads. The yoke is a cuboid, and each of the two long sides of the cuboid is provided with an opening, and each of the two short sides of the cuboid is provided with two first threaded holes; the first threaded holes are used for mounting binding posts and are connected with the direct-current stabilized power supply. The movable column head has an inverted L shape; the movable column head comprises a horizontal column head and a vertical column body; the horizontal column head is the upper end of the movable column head, and the vertical column body is the lower end of the movable column head, and the coil is sleeved on the vertical column body; the bottom surface of each vertical column body is provided with a second threaded hole, and a screw is connected from the bottom of the opening of the yoke to the second threaded hole in the bottom surface of the vertical column body; the movable column head is translated on the yoke to adjust the air gap between the two movable column heads.
[0010] Optionally, the signal acquisition and amplification module comprises a pre-stage amplification circuit and an analog-digital conversion circuit; the pre-stage amplification circuit is used for amplifying the uV-level abnormal Hall voltage signal to obtain an amplified abnormal Hall voltage signal; and the analog-digital conversion circuit is used for analog-digital converting the amplified abnormal Hall voltage signal to obtain a digital signal.
[0011] Optionally, the pre-stage amplification circuit adopts an AD8421 instrument amplifier.
[0012] Optionally, the analog-digital conversion circuit adopts an NI USB-6009 data acquisition card.
[0013] Optionally, the LabVIEW-based signal processing and analysis system is used for: The reference sine signal and the reference cosine signal with a phase difference of 90 degrees are generated; the digital signal is multiplied by the reference sine signal and the reference cosine signal respectively to obtain two orthogonal first product signals and second product signals; the first product signals and the second product signals are filtered to obtain filtered first product signals and filtered second product signals; and the final Hall voltage amplitude is calculated according to the filtered first product signals and the filtered second product signals.
[0014] Optionally, in the filtering process of the first product signals and the second product signals, the LabVIEW-based signal processing and analysis system is configured to filter the first product signals and the second product signals by using an IIR low-pass filter.
[0015] Optionally, the LabVIEW-based signal processing and analysis system is configured to store the final Hall voltage amplitude and the magnetic induction intensity in association and display a hysteresis loop.
[0016] Optionally, the wire diameter of the coil is 0.75 mm.
[0017] According to the embodiments provided in the present application, the following technical effects are disclosed: The present application provides an abnormal Hall effect comprehensive experiment platform for measuring a micro signal, a magnetic field generating module for generating a controllable magnetic field perpendicular to the surface of a sample to be measured, a signal acquisition and amplification module for acquiring a uV-level abnormal Hall voltage signal generated by the sample to be measured, and amplifying and analog-to-digital converting the uV-level abnormal Hall voltage signal to obtain a digital signal, and a LabVIEW-based signal processing and analysis system for running a digital quadrature phase-locked amplification algorithm to process the digital signal to obtain a final Hall voltage amplitude, and determining the magnetic induction intensity corresponding to the final Hall voltage amplitude according to the final Hall voltage amplitude and a pre-calibrated magnetic induction intensity and output voltage curve. The room temperature abnormal Hall effect is transferred to basic physics experiment teaching, the LabVIEW-based signal processing and analysis system uses LabVIEW to realize a digital quadrature phase-locked amplifier, and an experiment originally requiring large equipment such as a PPMS (Physical Property Measurement System, comprehensive physical property measurement system) is "miniaturized" to a desktop platform, the cost is reduced, and the high sensitivity of the digital phase-locked amplification integrated device in measuring the abnormal Hall effect micro voltage signal is improved. BRIEF DESCRIPTION OF DRAWINGS
[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.
[0019] Figure 1 A structural schematic diagram of an abnormal Hall effect comprehensive experimental platform for measuring a micro signal in an embodiment of the present application.
[0020] Figure 2 A structural schematic diagram of an electromagnet provided in an embodiment of the present application.
[0021] Figure 3 A processing flow schematic diagram of an abnormal Hall voltage signal provided in an embodiment of the present application.
[0022] Figure 4 A signal processing technical route schematic diagram provided in an embodiment of the present application.
[0023] Figure 5 A digital quadrature phase-locked amplification principle schematic diagram provided in an embodiment of the present application.
[0024] Figure 6 A LabVIEW-based phase-locked amplification program block diagram provided in an embodiment of the present application.
[0025] Figure 7 A LabVIEW-based magnetic field reading program design schematic diagram provided in an embodiment of the present application.
[0026] Figure 8 A LabVIEW-based magnetic field storage program design schematic diagram provided in an embodiment of the present application.
[0027] Figure 9 A LabVIEW-based abnormal Hall resistance value reading program design schematic diagram provided in an embodiment of the present application.
[0028] Figure 10 A LabVIEW-based abnormal Hall resistance value storage program design schematic diagram provided in an embodiment of the present application.
[0029] Figure 11 A LabVIEW-based magnetic induction intensity and abnormal Hall voltage storage array program design schematic diagram provided in an embodiment of the present application.
[0030] Figure 12 A LabVIEW-based hysteresis loop drawing program design schematic diagram provided in an embodiment of the present application.
[0031] Figure 13 The interactive interface design schematic diagram provided by an embodiment of the present application.
[0032] Figure 14 The orthogonal phase-locked step flowchart of the collected Hall signal provided by an embodiment of the present application.
[0033] Reference signs: Magnetic yoke - 1, moving stud - 2, opening - 3, first threaded hole - 4, terminal post - 5, cross stud - 6, vertical column body - 7, coil - 8, second threaded hole - 9. DETAILED DESCRIPTION
[0034] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.
[0035] The above purposes, features and advantages of the present application will be more obvious and easy to understand. The present application will be described in further detail below with reference to the drawings and specific embodiments.
[0036] In an exemplary embodiment, as shown in Figure 1 , a comprehensive experimental platform for measuring abnormal Hall effect of micro signals is provided, which includes a magnetic field generating module, a signal acquisition and amplification module, and a signal processing and analysis system based on LabVIEW, and can measure abnormal Hall signals of uV level with high sensitivity and extremely low cost.
[0037] (1) The magnetic field generating module is used to generate a controllable magnetic field perpendicular to the surface of the sample to be measured.
[0038] The magnetic field generating module includes an electromagnet and a direct current stabilized power supply for powering the electromagnet. The electromagnet includes a core and a coil 8 wound thereon, and the core has an adjustable air gap. The wire diameter of the coil 8 is 0.75 mm. The direction of the magnetic field generated by the electromagnet is perpendicular to the surface of the sample to be measured.
[0039] The overall view of the electromagnet is shown in Figure 2 (a), (b), and (c), the view from the bottom up is shown in Figure 2 (d), and the top view, left view, and front view of the electromagnet are shown in Figure 2 (e), (f), and (g), respectively.
[0040] The iron core comprises a yoke 1 and two movable column heads 2; the yoke 1 is a cuboid, two openings 3 are respectively arranged at two ends of the long side of the cuboid, and two first threaded holes 4 are respectively arranged at two short sides of the cuboid; the first threaded holes 4 are used for mounting connecting posts 5 and connecting with a direct-current stabilized power supply.
[0041] The movable column head 2 is in an inverted L shape; the movable column head 2 comprises a horizontal column head 6 and a vertical column body 7; the horizontal column head 6 is the upper end of the movable column head 2, the vertical column body 7 is the lower end of the movable column head 2, and a coil 8 is sleeved on the vertical column body 7; a second threaded hole 9 is arranged at the bottom surface of each vertical column body 7, and a screw is connected from the bottom to the top of the second threaded hole 9 at the bottom surface of the vertical column body 7 from the bottom of the opening 3 of the yoke 1; the movable column head 2 is translated on the yoke 1 to adjust the air gap between the two movable column heads 2, and the air gap between the two movable column heads 2 refers to the air gap between the two horizontal column heads 6; in experiments, a clamping device can be used to place a sample to be tested in the air gap between the two horizontal column heads 6; two edges of one end of the two horizontal column heads 6 close to each other are respectively provided with C chamfers.
[0042] The magnetic field generating module is composed of a coil 8 wound by a copper wire with a line diameter of 0.75 mm and an iron core made of No. 45 steel; the iron core is composed of a yoke 1 and two inverted L-shaped movable column heads 2; the air gap between the two inverted L-shaped movable column heads 2 is adjusted to limit the magnetic field strength within a suitable range; two M3 threaded holes are respectively arranged at two ends of the base (yoke 1), and a total of four connecting posts 5 are arranged to stably connect the coil 8; different colored connecting post 5 nuts are used to distinguish the same name ends; the excitation current matched with the electromagnet is provided by a numerical control adjustable direct-current stabilized power supply; after the fixed connecting post 5, the magnetic field strength is changed by adjusting the excitation current.
[0043] The signal acquisition and amplification module comprises a pre-amplification circuit and an analog-digital conversion circuit; the pre-amplification circuit is used for amplifying the uV-level abnormal Hall voltage signal to obtain an amplified abnormal Hall voltage signal; the analog-digital conversion circuit is used for analog-digital conversion of the amplified abnormal Hall voltage signal to obtain a digital signal.
[0044] The signal acquisition and amplification module comprises a pre-amplification circuit and an analog-digital conversion circuit; the pre-amplification circuit is used for amplifying the uV-level abnormal Hall voltage signal to obtain an amplified abnormal Hall voltage signal; the analog-digital conversion circuit is used for analog-digital conversion of the amplified abnormal Hall voltage signal to obtain a digital signal.
[0045] The pre-stage amplification circuit adopts AD8421 instrument amplifier. The model used in the application is an instrument amplifier with a gain range of 2-10000 and an input noise of 3nV / Hz. AD8421 is a high-speed instrument amplifier with ultra-low bias current, which has very high CMRR (Common-Mode Rejection Ratio), can restore low-level signals in the case of high-frequency common-mode noise, and has a high gain range of 2-10000. When the instrument amplifier is working, in order to eliminate the influence of power supply noise as much as possible, a low-ripple linear voltage regulator is used to supply power to the instrument amplifier, which provides a stable voltage of +10V and -10V.
[0046] The analog-to-digital conversion circuit adopts the built-in 14-bit ADC of NI USB-6009 data acquisition card. NI USB-6009 is a multifunctional data acquisition device with 8 analog input channels, 2 analog output channels and 12 digital I / O channels, and a built-in 32-bit counter. Its analog input resolution is up to 14 bits in differential mode and 13 bits in single-ended mode, with a maximum sampling rate of 48kS / s and an input range of ±10V. The analog output resolution is 12 bits, and the digital I / O channel is compatible with TTL / CMOS level. It is connected to the computer through USB2.0 interface and is plug and play, powered by USB bus. The signal conditioning circuit inside the NI USB-6009 data acquisition card contains a low-noise, high-input-impedance signal conditioning circuit, whose equivalent input impedance is completely independent of the sampling rate and is fixed at 144kΩ. At the same time, the input end integrates a filter with 40dB anti-aliasing suppression feature, without the need for external driving and filtering circuit.
[0047] In order to extract the uV-level weak abnormal Hall voltage signal in a low signal-to-noise ratio environment, high-precision signal acquisition is realized through the AD8421 instrument amplifier and the built-in 14-bit high-precision ADC of the NI USB-6009 data acquisition card.
[0048] As shown in Figure 3 The weak current signal of 0~50uA output by the numerical control alternating current constant current source generates a uV-level abnormal Hall voltage signal across the sample device under test. The signal is first amplified by 5000 times by the AD8421 instrument amplifier, and then enters the NI USB-6009 data acquisition card for analog-to-digital conversion. The converted digital signal is digitally phase-locked in LabVIEW, and the final result (taking the formed hysteresis loop as an example) is displayed on the interactive interface of the PC. The numerical control alternating current constant current source used in the application supports a module with a current of 100pA-50mA and a frequency adjustment of 1Hz-450Hz.
[0049] The magnetic induction intensity is collected by the Hall sensor integrated on the PCB board of the sample under test.
[0050] (Three) LabVIEW-based signal processing and analysis system, for: running digital quadrature phase-locked amplification algorithm, the digital signal is processed to get the final Hall voltage amplitude According to the final Hall voltage amplitude and the pre-calibrated magnetic induction intensity and output voltage curve, determine the final Hall voltage amplitude corresponding to the magnetic induction intensity.
[0051] The LabVIEW-based signal processing and analysis system is used to: generate two reference sinusoidal signals with a phase difference of 90 degrees; multiply the digital signal by the reference sinusoidal signal and the reference cosine signal respectively to obtain two orthogonal first product signals and second product signals; filter the first product signal and the second product signal to obtain filtered first product signal and filtered second product signal; calculate the final Hall voltage amplitude according to the filtered first product signal and the filtered second product signal.
[0052] As shown in Figure 14 After filtering the digital signal with an IIR bandpass filter, the filtered digital signal is multiplied by the reference sinusoidal signal and the reference cosine signal through a multiplier.
[0053] In terms of filtering the first product signal and the second product signal, the LabVIEW-based signal processing and analysis system is used to: filter the first product signal and the second product signal with an IIR low-pass filter.
[0054] In one specific example, a digital quadrature phase-locked amplifier is implemented on LabVIEW software, and before the step of multiplying the digital signal by the reference sinusoidal signal and the reference cosine signal, an IIR bandpass filter is used to filter the digital signal. The IIR bandpass filter and the IIR low-pass filter effectively filter out environmental noise and power frequency interference, recover the effective Hall voltage signal amplitude with high precision and high speed, and realize the extraction and processing of uV-level weak signals.
[0055] The signal processing technology route is shown in Figure 4 The signal processed by the pre-stage amplification circuit, the amplified abnormal Hall voltage signal and the corresponding magnetic field signal, through the NI USB-6009 data acquisition card into the program, are processed respectively to obtain the resistance value reflecting the Hall voltage size and the magnetic field intensity, and the hysteresis loop is drawn from it.
[0056] The quadrature phase-locked amplifier is a further optimization of the phase-locked amplifier. For a single-phase phase-locked amplifier, there is a certain relationship between the final amplitude and the phase: (1); wherein, is the time; is the time-dependent signal output by the system; is the gain of the system; is the amplitude of the digital signal; is the frequency of the digital signal; is the phase difference between the digital signal and the reference signal. It can be seen that in order to keep the measurement result reasonable, it is necessary to ensure that the phase difference between the digital signal and the reference signal does not change, which is difficult to achieve in an actual system.
[0057] The quadrature phase-locked amplifier can be regarded as two phase-locked amplifiers whose reference signals differ by 90 degrees. Let the input digital signal be: (2); wherein, is the digital signal (i.e. the input signal in Figure 5 ); is the frequency of the digital signal, is the initial phase, is random noise.
[0058] The reference signal is: (3); wherein: is the reference signal; is the amplitude of the reference signal, is the frequency of the reference signal, is the phase of the reference signal.
[0059] After the digital signal is multiplied and phase-shifted with the reference signal, a first product signal and a second product signal are obtained: (4); (5); wherein, the first product signal and the second product signal are orthogonal and differ by 90 degrees in phase, the first product signal and the second product signal are filtered through a low-pass filter, and after removing the high-frequency components, we obtain: (6); (7); wherein, is the filtered first product signal; is the filtered second product signal.
[0060] By squaring and taking the square root of the first and second filtered product signals, we can obtain the expression for the output signal and phase difference, which are unaffected by the phase difference, and the output Hall voltage. for: (8); The phase difference between the digital signal and the reference signal is: (9); The phase difference between the two reference signals is 90 degrees, therefore: (10); Equation (10) yields the final Hall voltage amplitude.
[0061] A quadrature phase-locked loop (PLL) is implemented in LabVIEW. The measurement signal is acquired through channel 1 differential mode of an NI USB-6009 acquisition card, and the reference signal is output through the LabVIEW signal generation VI. Since the signal source is the same, the phase difference accuracy between the two reference signals is well guaranteed. Quadrature PLL and low-pass digital filtering are then performed using sinusoidal signals with a 90-degree phase difference, and the final result is calculated. The LabVIEW-based PLL amplification program is as follows: Figure 6 As shown.
[0062] In magnetic field reading, the Hall sensor is connected to an analog input channel (channel 1) of the NI USB-6009 data acquisition card to read magnetic field data in real time. Using DAQmx, the settings are: Analog—Multi-channel—Multi-sampling—1D waveform, continuous sampling mode, sample count and rate per channel set to 1000, input terminal configuration set to single-ended mode RSE, physical channel selected as ai0, and source set to OnboardClock to obtain the acquired signal 1. This signal is then low-pass filtered to obtain the magnetic field signal, and the average value is calculated to obtain a relatively stable voltage value U. A linear expression for the magnetic flux density B and voltage value U is derived through calibration, and finally, the magnetic flux density B is calculated. The LabVIEW-based magnetic field reading and storage programming is as follows: Figure 7 and Figure 8 As shown. After connecting the Hall sensor to the NI USB-6009 data acquisition card, switch the channel to ai0 and run the program to read the data.
[0063] Similarly, in reading the anomalous Hall voltage U, the sample under test is connected to an analog input channel (channel 2) of the NI USB-6009 data acquisition card to read the anomalous Hall voltage data in real time. Using DAQmx, the settings are: Analog—Multi-channel—Multi-sampling—1D waveform, continuous sampling mode, sample count and rate per channel set to 48000 (corresponding to the reference signal), differential input terminal configuration, ai2 physical channel selection, and OnboardClock source to obtain the acquired signal 2. This signal is then subjected to quadrature phase-locked loop and filtering, and the average value is calculated to obtain a relatively stable voltage amplitude. The LabVIEW anomalous Hall resistance value reading and storage program design is as follows: Figure 9 and Figure 10 As shown. After connecting the sample to the NI USB-6009 data acquisition card, switch the channel to ai2, set the frequency of the reference signal, and run the program to read the data.
[0064] After real-time reading of the magnetic flux density B and anomalous Hall voltage U, an event-driven structure is adopted. When the corresponding button is pressed, the data at that moment is stored, and the coordinate value of that point is obtained. The measurement continues after changing the magnetic field strength. Finally, the obtained data is integrated into two arrays: a magnetic flux density array and an anomalous Hall voltage array. The data is stored in a specified text file and plotted using an XY graph. The program design for storing the magnetic flux density and anomalous Hall voltage arrays based on LabVIEW is as follows: Figure 11 As shown, the programming for drawing hysteresis loops based on LabVIEW is as follows: Figure 12 As shown.
[0065] The LabVIEW-based signal processing and analysis system is used to: associate and store the synchronously acquired final Hall voltage amplitude with the magnetic induction intensity, and draw it as a hysteresis loop for display.
[0066] Interactive interface such as Figure 13 As shown, this design and construction is based on LabVIEW. Its main functions include real-time display of the magnetic field strength and anomalous Hall signal changes over time; manual input of the magnitude and frequency of the driving current to be applied to the sample; plotting the change curve of the anomalous Hall voltage V of the sample based on the measurement data; and displaying historical experimental measurement data.
[0067] Selecting channel 1 will display the magnetic field signal and corresponding U and B values on the front panel after the program runs. Pressing the save button will save the magnetic induction intensity data B. Selecting channel 2 allows you to set the range of the NI USB-6009 data acquisition card and the frequency of the reference signal. After the program runs, the Hall signal, recovery signal, and anomalous Hall voltage V value will be displayed on the front panel. Pressing the save button will save the anomalous Hall voltage data V. Switching tabs displays the specific data collected in this measurement. Each set of data will generate a corresponding point on the graph. If 50 sets of data are measured in one measurement, the graph will plot 50 points, which will be connected sequentially to form a hysteresis loop. When a measurement in the experiment is completed, you can close the interface, and the data table will be cleared of all recorded data for the next experiment.
[0068] The anomalous Hall effect integrated experimental platform provided in this application for measuring minute signals is an experimental platform for studying the anomalous Hall effect under room temperature conditions. Based on LabVIEW's lock-in program and combined with front-end hardware, it realizes a high-sensitivity, low-cost digital lock-in amplifier that can detect weak voltage signals at the microvolt level.
[0069] This application utilizes LabVIEW software to implement a digital quadrature lock-in amplifier, offering several advantages. Firstly, digital filters, compared to analog filters, can achieve a narrower passband and a lower cutoff frequency, reducing it to below 0.5Hz, better meeting measurement requirements. Secondly, digital circuits exhibit stronger anti-interference capabilities and greater stability than analog circuits, are less affected by environmental factors such as temperature and voltage, and are easier to modify. They can be further calibrated through programming, facilitating the system's testing process.
[0070] This experimental platform can transfer the room-temperature anomalous Hall effect to basic physics experimental teaching. The anomalous Hall effect experiment has been introduced from graduate students' scientific research experiments to university physics experiments for undergraduates. The experiment, which originally required large equipment such as PPMS, has been "miniaturized" to a desktop platform, reducing the cost to 1 / 200 and meeting the accuracy requirements of physics experiments.
[0071] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0072] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.
Claims
1. An abnormal Hall effect comprehensive experiment platform for measuring a micro signal, characterized in that, The abnormal Hall effect comprehensive experiment platform for measuring a micro signal comprises: a magnetic field generating module for generating a controllable magnetic field perpendicular to a surface of a sample to be measured; a signal acquisition and amplification module for acquiring a uV-level abnormal Hall voltage signal generated by the sample to be measured, amplifying and analog-digital converting the uV-level abnormal Hall voltage signal, and obtaining a digital signal; a LabVIEW-based signal processing and analysis system for: running a digital quadrature phase-locked amplification algorithm, processing the digital signal, and obtaining a final Hall voltage amplitude; and determining a magnetic induction intensity corresponding to the final Hall voltage amplitude according to the final Hall voltage amplitude and a pre-calibrated magnetic induction intensity-output voltage curve. 2.The abnormal Hall effect comprehensive experiment platform for measuring micro signals according to claim 1, wherein, The magnetic field generating module comprises an electromagnet and a direct-current stabilized power supply for powering the electromagnet; the electromagnet comprises a core and a coil wound on the core, and the core has an adjustable air gap.
3. The abnormal Hall effect comprehensive experiment platform for measuring a micro signal according to claim 2, characterized in that, The core comprises a yoke and two movable column heads. The yoke is a cuboid, and each end of the long side of the cuboid is provided with an opening, and each of the two short sides of the cuboid is provided with two first threaded holes; the first threaded holes are used for mounting binding posts and are connected with the direct-current stabilized power supply; The movable column head has an inverted L shape; the movable column head comprises a horizontal column head and a vertical column body; the horizontal column head is the upper end of the movable column head, and the vertical column body is the lower end of the movable column head, and the coil is sleeved on the vertical column body; the bottom surface of each vertical column body is provided with a second threaded hole, and a screw is connected from the bottom of the opening of the yoke to the second threaded hole in the bottom surface of the vertical column body; the movable column head translates on the yoke to adjust the air gap between the two movable column heads.
4. The abnormal Hall effect comprehensive experiment platform for measuring a micro signal according to claim 1, characterized in that, The signal acquisition and amplification module comprises a pre-stage amplification circuit and an analog-digital conversion circuit; the pre-stage amplification circuit is used for amplifying the uV-level abnormal Hall voltage signal to obtain an amplified abnormal Hall voltage signal; The analog-digital conversion circuit is used for analog-digital converting the amplified abnormal Hall voltage signal to obtain a digital signal.
5. The abnormal Hall effect comprehensive experiment platform for measuring a micro signal according to claim 4, characterized in that, The pre-stage amplification circuit adopts an AD8421 instrument amplifier.
6. The abnormal Hall effect comprehensive experiment platform for measuring a micro signal according to claim 4, characterized in that, The analog-digital conversion circuit adopts an NI USB-6009 data acquisition card.
7. The abnormal Hall effect comprehensive experiment platform for measuring a micro signal according to claim 1, characterized in that, The LabVIEW-based signal processing and analysis system is used for: generating two reference sinusoidal signals with a phase difference of 90 degrees; multiplying the digital signal with the reference sinusoidal signals to obtain two first and second product signals which are in quadrature; filtering the first and second product signals to obtain filtered first and second product signals; and calculating the final Hall voltage amplitude according to the filtered first and second product signals.
8. The abnormal Hall effect comprehensive experiment platform for measuring a micro signal according to claim 7, characterized in that, In terms of filtering the first and second product signals, the LabVIEW-based signal processing and analysis system is used for filtering the first and second product signals by using an IIR low-pass filter.
9. The abnormal Hall effect comprehensive experiment platform for measuring a micro signal according to claim 1, characterized in that, The LabVIEW-based signal processing and analysis system is used for: storing the final Hall voltage amplitude and the magnetic induction intensity which are synchronously acquired in association and drawing a hysteresis loop for display.
10. The abnormal Hall effect comprehensive experiment platform for measuring a micro signal according to claim 3, characterized in that, The wire diameter of the coil is 0.75 mm.