Hall measuring system with rotating magnetic field

Abstract

A measuring system with a rotating magnetic field for observing the Hall effect or the photoelectromagnetic effect in a test unit (2052), the measuring system comprising: a motor-driven first magnet (201); a freely rotating second magnet (204) rotating with the first magnet (201) in a master-slave configuration, wherein driving the first magnet (201) and its resulting rotation drives a corresponding rotation of the second magnet (204); a test unit table (205) insertable between the first magnet (201) and the second magnet (204), on which the test unit (2052) is available in a first or second orientation; Control units (206, 207) arranged to center the test unit table (205) between the first magnet (201) and the second magnet (204); and orthogonal magnetic field sensors (250, 260) arranged to enable positional initialization of the first magnet (201) and the second magnet (204) and to generate in-phase and out-of-phase reference signals for phase-sensitive or lock-in signal detection.

Description

BACKGROUND

[0001] The present invention relates generally to measurement techniques and more specifically to a Hall effect measurement system using a rotating magnet.

[0002] A Hall measurement is a characterization technique that can be used in a variety of applications, such as research on semiconductors and solid-state devices. A Hall measurement allows for a measurement of a free carrier density, which can yield carrier mobility when considered in conjunction with a measurement of electrical resistivity. The so-called Hall effect occurs when a current is passed through a material with an applied perpendicular magnetic field, resulting in a Hall voltage V H is generated as provided in Equation No. 1 as follows: VH=Bl / nde

[0003] In equation 1 above, B is the magnetic field, / is the electric current flowing through the sample, n is the density of free charge carriers, d is the sample thickness, and e is the charge of an electron.

[0004] A performance figure in the Hall measurement is the Hall angle φ, whose tangent is the ratio between the Hall or transverse resistance (R xy ) and the series resistance (R xx ). The tangent of this Hall angle can be given in the case of a quadratic sample by equation 2 as follows: Tan φ=Rxy / Rxx=Bμ

[0005] In equation 2 above, µ is the mobility of the majority carrier.

[0006] A good or quality Hall measurement requires a sufficiently high Hall angle or tan φ around a value of unity. Based on equation 2, a problem may arise if a sample has poor mobility (e.g., µ << 1 cm 2 / Vs) or the available magnetic field is limited (e.g., B << 0.1 Tesla). Furthermore, based on equation 1, samples with a very high carrier density n can also have a small Hall voltage V H Some measurement environments, such as low temperature measurement, require the use of a very small excitation current / , which thus results in a small Hall voltage V H In such situations, a DC magnetic field Hall measurement can produce a small Hall voltage V H which is hidden within a DC voltage offset due to a geometric sample asymmetry. The asymmetry can cause mixing of the Hall or shunt resistance (R xy) and the series resistance (R xx ) cause.

[0007] US 2014 / 0 028 305 A1 discloses a system comprising a motor configured to rotate at least one magnet at a first frequency, a sensor configured to generate a reference signal of the rotation of the at least one magnet, and a lock-in detection system configured to receive the reference signal, supply an excitation current at a second frequency to a device under test, measure a voltage from the device under test, demodulate the second frequency, and demodulate the first frequency from the measured voltage using the reference signal to obtain a Hall voltage associated with the device under test.

[0008] The scientific publication "A parallel dipole line system" by O. Gunawan et al., published in 2015 in Appl. Phys. Lett., vol. 106, issue 6, pp. 062407-1 to 062407-5, presents a study of a measurement system for highly sensitive Hall measurements. It uses a pair of cylindrical magnets to generate a rotating magnetic field diametrically between the magnets at the sample location and records the measurement signal using lock-in detection. The magnets form a master-slave configuration in which the lower magnet can be rotated about its cylindrical axis by a stepper motor via a gear system, and the upper magnet, which is vertically adjustable and rotatably mounted on its cylindrical axis, assumes a rotational position determined by the orientation of the magnetic field of the driven magnet, which corresponds to the current rotational position. A Hall sensor is installed on a mounting plate below the lower magnet.

[0009] JP 2003 207 365 A discloses a rotation angle sensor for a rotatably mounted magnet, comprising two Hall elements that form a right angle with the magnet's rotation axis. The Hall elements are connected to a control circuit that calculates the position of the rotatably mounted magnet from the output signals of the Hall elements.

[0010] US 2002 / 0 179 825 A1 discloses a non-contact linear output angular position sensor for a rotatable arc segment magnet arranged to rotate around the stationary components of the sensor, which comprise a pair of stationary flux concentrators separated by a Hall probe.

[0011] The following description is also related to the description of U.S. Patent No. 8,895,355 (Cao). SUMMARY

[0012] According to a particular embodiment of the present invention, a rotating magnetic field measuring system for observing the Hall effect or the photoelectromagnetic effect in a device under test is provided, the measuring system comprising: a motor-driven first magnet; a freely rotating second magnet rotating with the first magnet in a master-slave configuration, wherein driving the first magnet and its resulting rotation drives a corresponding rotation of the second magnet; a test unit table insertable between the first magnet and the second magnet, on which the test unit is available in a first or second orientation; Control units arranged to center the test unit table between the first magnet and the second magnet; and orthogonal magnetic field sensors arranged to allow positional initialization of the first magnet and the second magnet and to generate in-phase and out-of-phase reference signals for phase-sensitive or lock-in signal detection.

[0013] According to a further embodiment of the present invention, the first magnet comprises a motor-driven cylindrical magnet with transverse magnetization; the second magnet comprises a freely rotating cylindrical magnet that rotates with the motor-driven magnet, and the control units comprise a first control unit and a second control unit, wherein the first control unit is arranged to maneuver the motor-driven magnet, wherein the second control unit is arranged to maneuver the test unit table.

[0014] According to another embodiment of the present invention, there is now provided a method for operating a rotating magnetic field measuring system for observing the Hall effect or the photoelectromagnetic effect in a device under test, the method comprising: Arranging a motor-driven first magnet and a freely rotating second magnet in a master-slave configuration, wherein driving the first magnet and its resulting rotation drives a corresponding rotation of the second magnet; Inserting a test unit table between the first magnet and the second magnet; Arranging the test unit on the test unit table in a first or a second orientation; Centering the test unit table between the first magnet and the second magnet; Arranging orthogonal magnetic field sensors to enable positional initialization of the first magnet and the second magnet; and Use the orthogonal magnetic field sensors to generate in-phase and out-of-phase reference signals for phase-sensitive or lock-in signal acquisition.

[0015] According to yet another embodiment of the present invention, a data processing system is provided, comprising a processor and a memory on which a program is stored which, when executed, causes the processor to perform the method for operating a rotating magnetic field measuring system according to one embodiment.

[0016] Further features and advantages of the invention are realized by the techniques of the present invention. Further embodiments and aspects of the invention are described in detail herein and are considered part of the claimed invention. For a better understanding of the invention, including its advantages and features, reference should be made to the description and drawings.

[0017] The objects underlying the invention are achieved with the features of the independent patent claims. Embodiments of the invention are the subject of the dependent patent claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: Fig. 1 is a schematic diagram illustrating a data processing system according to embodiments of the present invention; Fig. 2 is a side view of a rotating magnetic field measurement system according to embodiments of the present invention; Fig. 3 is a front view of a rotating magnetic field measurement system according to embodiments of the present invention; Fig. Figure 4A is a graphical illustration of magnet initialization and field detection; Fig. Figure 4B is a graphical illustration of magnet initialization and field detection; Fig. 5A is a graphical illustration of a magnetic field determination on a device under test; Fig. 5B is a graphical illustration of a magnetic field determination on a device under test; Fig. 6 is a flowchart illustrating a method of operating the rotating magnetic field measuring system of Fig. 1 and Fig. 2 illustrates; and Fig. 7 is an exemplary screenshot generated by control software according to embodiments of the present invention. DETAILED DESCRIPTION

[0019] As described below, a rotating magnetic field measurement system is provided for observing the Hall effect or the photoelectromagnetic effect with high sensitivity. Targeting materials with very low carrier mobility, very thin samples, and samples with very low or very high carrier density, the system includes a pair of rotating magnets, one driven by a motor drive and another that rotates freely and can be positioned by a linear actuator turret, magnetic focusing parts, a manipulator for positioning the sample, a light source for illuminating the sample, a mechanical platform with connector panels, and a housing shield. The system is connected to a motor control box and a switching matrix system and is controlled by a computer.Software that performs signal processing (power spectral density and lock-in detection) is used to extract the final Hall or PEM signal. The system can also be used to improve the signal-to-noise ratio of any experiment involving a magnetic field.

[0020] Referring to Fig. 1, an exemplary data processing system 100 is shown. The system 100 is shown as including a memory 102. Stored in the memory 102 are executable instructions, which may be stored in any manner and at any level of abstraction, such as in association with one or more processes, routines, methods, etc. As an example, at least a portion of the instructions are embodied in Fig. 1 as being associated with a first program 104a and a second program 104b.

[0021] The instructions stored in memory 102 may be executed by one or more processors, such as processor 106. Processor 106 may be coupled to one or more input / output (I / O) devices 108 and include a signal conditioning system 1061 for data selection and background subtraction, a power spectral density analysis system 1062, and a system for lock-in detection and signal-to-noise ratio calculation 1063. In some embodiments, the one or more I / O devices 108 may include one or more of a keyboard, a touchscreen, a display screen, a microphone, a speaker, a mouse, a button or key, a remote control, a joystick, a printer, etc.The one or more I / O units 108 may be configured to provide an interface to allow a user to interact with the system 100. The system 100 is illustrative. In some embodiments of the present invention, one or more of the entities may be optional. In some embodiments of the present invention, additional entities not shown may be included. For example, in some embodiments, the system 100 may be associated with one or more networks that may be communicatively interconnected via one or more switches, routers, or the like. In some embodiments, the entities may be configured in a manner different from that shown in FIG. Fig. 1 shown be arranged or organized in a distinctive manner. One or more of the Fig. 1 may be associated with one or more of the units or entities described herein.

[0022] Fig. 2 and Fig. 3 illustrate a system architecture 200 that can be used as a Hall effect measurement system with rotating magnets. The architecture 200 can be used in conjunction with one or more units or entities, such as those described above in connection with the system 100 of Fig. 1 described units and entities, be operational. As in Fig. 2 and Fig. 3, the architecture 200 may be provided as a rotating magnetic field Hall effect measurement system and includes a first or motor-driven cylindrical magnet 201 rotationally driven by a motor 202 via a gearbox 203, a second or freely rotating cylindrical magnet 204 rotating with the motor-driven magnet 201 in a master-slave configuration where driving the motor-driven magnet 201 and its resulting rotation drives a corresponding rotation of the freely rotating magnet 204, a test unit stage 205, first and second control units 206 and 207, and an orthogonal magnetic field sensor system. The motor-driven magnet 201 and the freely rotating magnet 204 may each be cylindrical magnets with a transverse (diameter) magnetization (i.e., magnetization along the diameter).They form a rotating master-slave magnet system that produces several important characteristics, including a unidirectional field at the center of the DUT 2052 (to be described below), a high purity single harmonic field oscillation, and strong magnetic fields (i.e., around ≈ 2 T peak to peak).

[0023] The DUT table 205 is insertable between the motor-driven magnet 201 and the freely rotating magnet 204 and has a surface on which a DUT 2052 is available. The DUT 2052 may be provided as a Hall or van der Pauw probe with four or more terminals for receiving current and mounted in a first or second orientation. For example, when the DUT 2052 is mounted horizontally, the DUT 2052 may be positioned for a Hall measurement. In contrast, as another example, when the DUT 2052 is mounted vertically, the DUT 2052 may be positioned for testing using the photoelectromagnetic effect (PEM) with light coming from one side, as described below.

[0024] The first control unit 206 is provided as a magnet tower 210 and arranged to maneuver at least one of the motor-driven magnet 201 and the freely rotating magnet 204 in at least a first direction, such as a vertical or Z-axis direction. The second control unit 207 is provided as a table tower 220 and arranged to maneuver the test unit table 205 in the first direction as well as a second and a third direction, such as lateral or X- and Y-axis directions. According to embodiments, both the magnet tower 210 and the table tower 220 may be attached to a platform 230 that is substantially planar so that they stand side by side with a relatively small distance between them. The motor 202 may also be attached to the platform 230 for support.The magnet tower 210 and the table tower 220 are both elongated features that extend from the platform 230 in the first direction (i.e., upward).

[0025] The magnet tower 210 includes a ruler feature 211 that allows measurement of a distance between the motor-driven magnet 201 and the freely rotating magnet 204, and between each magnet and the test unit table 205 or the test unit 2052. A stop 240 is also attached to the platform 230 to limit a distance that the freely rotating magnet 204 can travel. The stop 240 includes a threaded shaft and a correspondingly threaded stop member that can be rotated about the shaft to assume a predefined position. In this position, an upper surface of the stop member serves as a mechanical interaction unit that prevents movement of the freely rotating magnet 204 toward the test unit 2052 beyond a given distance.

[0026] According to embodiments of the present invention, the motor-driven magnet 201 is a cylindrical magnet rotatably mounted on a drive shaft 2010 extending from the gearbox 203 to a support feature attached to the platform 230 to define a first axis of rotation. The motor-driven magnet 201 thus rotates about the first axis of rotation according to rotational drive inputs provided by the motor 202 via the gearbox 203. The freely rotating magnet 204 is a cylindrical magnet rotatably mounted on a shaft 2040 extending through the freely rotating magnet 204 between support flanges attached to the magnet tower 210 to define a second axis of rotation about which the freely rotating magnet 204 rotates.The motor-driven magnet 201 and the freely rotating magnet 204 may be substantially parallel to each other, with the first and second axes of rotation correspondingly substantially parallel to each other. The freely rotating magnet 204 rotates as a result of its interaction with the magnetic field generated by the rotation of the motor-driven magnet 201.

[0027] The orthogonal magnetic field sensor system includes a first sensor 250 and a second sensor 260. The first sensor 250 is located at an outer end of a tip and can be arranged to face a downwardly facing (i.e., non-longitudinal) lateral surface of the motor-driven magnet 201. Thus, the first sensor 250 can face upwardly in the first direction. The second sensor 260 is located at an outer end of the tip and can be arranged to face a sideways transverse side of the motor-driven magnet 201. Thus, the second sensor 260 can face sideways in either the second or third direction. In either case, the first sensor 201 and the second sensor 204 cooperatively enable positional initialization of the motor-driven magnet 201 and possibly the freely rotating magnet 204.The first sensor 201 and the second sensor 204 may be further configured to generate in-phase and out-of-phase reference signals for phase-sensitive or lock-in Hall signal detection operations.

[0028] When the motor-driven magnet 201 rotates about the first rotation axis, the motor-driven magnet 201 generates a magnetic field in the vicinity of the test unit table 205. Similarly, when the freely rotating magnet 204 rotates about the second rotation axis, the freely rotating magnet 204 generates a magnetic field in the vicinity of the test unit table 205. At least one or both of these two magnetic fields can be enhanced in some cases by the presence of a magnetic flux concentrator. The magnetic flux concentrator can be provided as a first magnetic flux concentrator 270 and a second magnetic field concentrator 271. The first magnetic field concentrator 270 is interposed between the motor-driven magnet 201 and the bottom surface of the test unit table 205.In contrast, the second magnetic flux concentrator 271 is inserted between the freely rotating magnet 204 and the test unit table 205 or an upper surface of the test unit 2052 itself.

[0029] According to embodiments of the present invention, the first and second magnetic flux concentrators 270 and 271 may be formed from a high permeability material, such as a material containing iron-nickel or alloys thereof.

[0030] Still referring to Fig. 2 and Fig. 3, the architecture 200 may further include a light source 280 and a contact terminal 290. The light source 280 is supported on an outer end of a support member 281 attached to the platform 230 and is arranged to emit light toward the device under test 2052 for performing a PEM operation. The contact terminal 290 may be attached directly to the platform 230 and serves to provide and conduct power to the device under test 2052 during test operations.

[0031] With reference to Fig. 4A to 7 can be achieved by the architecture 200 of Fig. 1 and Fig. 2 can be operated in a first or a second mode. The first mode is a static (i.e., direct current or DC) magnetic field mode or a standard static field measurement system in which the field on the device under test 2052 is kept stationary (e.g., +- B max, 0) and a Hall measurement is performed. The second mode is a continuously rotating (i.e., alternating current or AC) field mode, in which the field continuously rotates and a Hall measurement is performed. As noted above, during the second mode, the orthogonal magnetic field sensor system initializes magnetic field positions to determine a zero angle (θ = 0) at which the magnetic field on the device under test 2052 is at a maximum. This position can be more accurately determined by monitoring when the second sensor 260 is at a zero angle because at this position the first sensor 250 is near the maximum.

[0032] An operation of the architecture is now described in the understanding that it is important to determine an amplitude of a field oscillation (B max) on the test unit 2052 as accurately as possible, since it affects the accuracy of the Hall measurement. When the motor-driven and freely rotating magnets 201 and 204 rotate and the corresponding magnetic fields rotate, a phase angle of at least the motor-driven magnet 201 is given as: θ = ω REF t, where ω = 2πf REF and f REF is a reference rotation frequency and t is time. The reference magnetic field on the test unit 2052 is given as: BREF(t)=Bmaxcos(ωREFt) B max is an average field across the test unit 2052 and depends on the gap g between the motor-driven and freely rotating magnets 201 and 204 and a size s of the test unit 2052. The gap g can be determined by reading the ruler feature 211 on the magnet tower 210. B maxcan be determined using the equation of a magnetic field of a diametrical magnet. Assuming that a test piece 2052 of size sxs is placed in the YZ plane at the center of the gap g, the field is given as: v2=(g / 2−acosϕ)2+(y−asinϕ)2 BM(y,z)=μ0Ma2π∫02π∑n=1.2(−1)n(g / 2−acosϕ)cosϕun2+v2+unun2+v2dϕx^ u1,2=z±L / 2

[0033] The average maximum field is averaged over the sample size: Bmax(g,s)=∫BM(y,z)dydz / s2

[0034] Examples of magnetic field determination are shown in the diagrams of Fig. 5A and Fig. 5B. Fig. Figure 5A shows that B max decreases with increasing gap g, and Fig. Figure 5B also shows that B max decreases as the size s of the test unit 2052 increases. Thus, B maxfor given values ​​of magnet magnetization M, length L, radius a, gap g and size s of the test piece unit 2052 using these diagrams or the equations given above.

[0035] With further reference to Fig. 1 and with additional reference to Fig. 6 and Fig. 7 and understanding that the processor 106 and the one or more I / O devices may be used to control and communicate with the various components of the architecture 200, and that at least one or both of the first program 104a and a second program 104b may be configured as control software for managing the various components of the architecture 200, the control software may execute a method. The method begins with the device under test 2052 being mounted generally at a center of the device under test table 205 (operation 600), with a measurement of the gap g and the size s of the device under test 2052 to B max to be determined (Procedure 601), and with a measurement of a contact resistance (R C ) and a sheet resistance (R S ) of the test unit 2052 (operation 602). The procedure continues with a measurement of a Hall resistance (R XY) and selecting a motor frequency f REF and a sample stream I S for the motor-driven magnet 201 (operation 603), rotating the motor-driven magnet 201 and recording the Hall resistance (R xy ) and the field sensor B REF over time (process 604) and processing the Hall signal (R xy ) by means of background subtraction and spectral power analysis (operation 605).

[0036] For processing the Hall signal (R xy) of operation 605, manual or automatic raw data selection is performed to avoid transient or spiky signals that may be detrimental to the final outputs of the phase-sensitive detector, background data is removed, Fourier transform (FT) and power-spectral-density (PSD) analyses are performed to allow numerical phase-sensitive acquisition / lock-in analysis of the raw signal, and signal-to-noise ratio (S / N) calculation.

[0037] The raw reverb signal is given as: RXY(t)=Bmaxcosωtnde+BmaxωAIssin ωt+αRXX+N(t) where R XY is the raw shunt resistance or the Hall signal, R XX is the series resistance, n is a carrier density, d is the thickness of the test piece unit 2052, e is an electron charge, A is an effective loop area, I Sis a current source running through the test unit 2052, α is a component of R XX which, due to the asymmetry of the test unit 2052 in R XY appears (0 < α < 1), and N(t) is noise or the rest of the signal.

[0038] The control software then performs a numerical stepwise acquisition to separate the in-phase signal X (the desired Hall signal) and the out-of-phase signal Y (parasitic electromotive force voltage), given as: X(t)=2T∫t−TtRXY(t)cosωREFtdt Y(t)=2T∫t−TtRXY(t)sinωREFtdt where T is the integration time equal to a multiple of the lock-in time constant, which can be adjusted by the signal processing software.

[0039] The Hall signal must then be inspected in the frequency domain to see if there is a signal at f REFFor this purpose, Fourier transform and power spectral density (PSD) analyses are performed. A PSD analysis enhances the periodicity (i.e., the desired Hall signal) in the raw signal, since PSD can be equal to a Fourier transform of a signal's autocorrelation. The software then calculates and generates a report of the final results, including the S / N ratio of the measurement.

[0040] X = Bmax / nde, Y = BmaxwA / IS, n = Bmax / Xde, µ = 1 / neρ, where ρ is the specific electrical resistance of the sample, which can be obtained from a longitudinal Van der Pauw measurement. The signal-to-noise ratio is given as: S / N = <X(t) 2 > / <R XY 2 (t)>.

[0041] To Fig. 6, the method thus includes determining whether the Hall power spectral density (PSD) has a peak located at f REFis present (operation 606). In a case where the Hall power spectral density (PSD) does not have a peak located at f REF , is present, the method then includes increasing an acquisition time or correcting a faulty contact / unit (operation 607), after which control returns to operation 602. Alternatively, in a case where the Hall power spectral density (PSD) has a peak occurring at f REF is present, performing a lock-in acquisition to the Hall signal with extraction of in-phase (X) and out-of-phase (Y) signal components and calculating a signal-to-noise ratio (S / N) (operation 608).

[0042] Once operation 608 is complete, a determination is made as to whether the out-of-phase (Y) signal is much greater than the in-phase (X) signal (operation 609). In a case where the out-of-phase (Y) signal is determined to be much greater than the in-phase (X) signal, the motor frequency f REF reduced or the sample current I S is increased (operation 610), and control returns to operation 603. Alternatively, in a case where the out-of-phase (Y) signal is determined to be not much larger than the in-phase (X) signal, final results are calculated (operation 611). The final results concern whether the device under test 2052 is an N- or P-type carrier, as well as the carrier mobility and carrier density.

[0043] As in Fig.7, the control software may also generate a user interface 700 on a display unit through which a user can at least monitor the Hall measurement. Such a user interface 700 may include at least a readout of the magnetic field 701 in and around the device under test 2052, a readout of the magnetic field with a Fourier transform 702 applied thereto, the raw Hall signal R XY 703, the Hall power spectral density (PSD) 704 for checking the validity of the Hall raw signal R XY 703, the lock-in output X, Y and S / N 705 and an adjustable lock-in time constant 706.

[0044] The terminology used herein is for the purpose of describing particular embodiments of the present invention and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an", "the", "the", and their declensions are intended to include the plural forms as well, unless the context clearly indicates otherwise. It is further understood that the terms "comprises" and / or "comprising", when used herein, indicate the presence of stated features, units, steps, acts, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, units, steps, acts, operations, elements, components, and / or groups thereof.

[0045] The corresponding structures, materials, acts, and equivalents of all means or steps and functional elements in the following claims are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed. Many changes and variations will be apparent to those skilled in the art without departing from the scope of the invention.The embodiments of the present invention were chosen to best describe the principles of the invention and its practical application and to enable others skilled in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.

[0046] The flowcharts depicted herein are merely exemplary. Many variations may be made to this diagram or the steps (or acts or operations) described therein without departing from the spirit of the invention. For example, the steps may be performed in a different order, or steps may be added, removed, or altered. All such variations are considered part of the claimed invention.

[0047] While the preferred embodiment of the invention has been described, it is to be understood that those skilled in the art may now and in the future make various improvements and enhancements that fall within the scope of the claims that follow. These claims should be construed to provide the proper protection for the invention first described.

Claims

[1] A rotating magnetic field measuring system for observing the Hall effect or the photoelectromagnetic effect in a device under test (2052), the measuring system comprising: a motor-driven first magnet (201); a freely rotating second magnet (204) rotating with the first magnet (201) in a master-slave configuration, wherein driving the first magnet (201) and its resulting rotation drives a corresponding rotation of the second magnet (204); a test unit table (205) insertable between the first magnet (201) and the second magnet (204), on which the test unit (2052) is available in a first or second orientation; Control units (206, 207) arranged to center the test unit table (205) between the first magnet (201) and the second magnet (204); and orthogonal magnetic field sensors (250, 260) arranged to enable positional initialization of the first magnet (201) and the second magnet (204) and to generate in-phase and out-of-phase reference signals for phase-sensitive or lock-in signal detection. [2] The measuring system of claim 1, wherein the magnetic field sensors (250, 260) are arranged adjacent to non-longitudinal sides of the first magnet (201). [3] Measuring system according to claim 1, wherein: the first magnet (201) comprises a motor-driven cylindrical magnet with transverse magnetization; the second magnet (204) comprises a freely rotating cylindrical magnet that rotates with the motor-driven magnet, and the control units (206, 207) comprise a first control unit (206) and a second control unit (207), wherein the first control unit (206) is arranged to maneuver the motor-driven magnet, wherein the second control unit (207) is arranged to maneuver the test unit table (205). [4] Measuring system according to one of the preceding claims, wherein the first magnet (201) and the second magnet (204) are arranged in parallel. [5] The measuring system of any preceding claim, further comprising a magnetic flux concentrator (270, 271) for increasing a magnetic field of either the first magnet (201) or the second magnet (204). [6] The measuring system according to claim 5, wherein the magnetic flux concentrator (270, 271) is provided as a first magnetic flux concentrator (270) inserted between the first magnet (201) and the test unit table (205) and a second magnetic flux concentrator (271) inserted between the second magnet (204) and the test unit table (205). [7] The measuring system of claim 5, wherein the magnetic flux concentrator (270, 271) comprises a material containing iron-nickel or alloys thereof. [8] A measuring system according to any one of the preceding claims, further comprising a light source (280) arranged to emit light towards the device under test (2052). [9] A measurement system according to any one of the preceding claims, wherein the device under test (2052) comprises a Hall or Van der Pauw probe having four or more terminals for receiving current and further comprising a contact terminal board (290) arranged to apply current to the device under test (2052). [10] The measuring system of claim 3, wherein the first control unit (206) maneuvers the motor-driven magnet in a first direction and the second control unit (207) maneuvers the test unit table (205) in the first and a second and third direction. [11] The measuring system of claim 10, further comprising a stop (240) arranged to limit movement of the freely rotating magnet in the first direction. [12] The measuring system of claim 10, further comprising a ruler (211) for determining a distance in the first direction between the motor-driven magnet and the freely rotating magnet. [13] The measuring system of claim 3, wherein the orthogonal magnetic field sensors (250, 260) are arranged adjacent to non-longitudinal sides of the motor-driven magnet. [14] A method for operating a rotating magnetic field measuring system for observing the Hall effect or the photoelectromagnetic effect in a device under test (2052), the method comprising: Arranging a motor-driven first magnet (201) and a freely rotating second magnet (204) in a master-slave configuration, wherein driving the first magnet (201) and its resulting rotation drives a corresponding rotation of the second magnet (204); inserting a test unit table (205) between the first magnet (201) and the second magnet (204); Arranging the test unit (2052) on the test unit table (205) in a first or a second orientation; Centering the test unit table (205) between the first magnet (201) and the second magnet (204); Arranging orthogonal magnetic field sensors (250, 260) so as to enable positional initialization of the first magnet (201) and the second magnet (204); and Using the magnetic field sensors (250, 260) to generate in-phase and out-of-phase reference signals for phase-sensitive or lock-in signal detection. [15] The method of claim 14, further comprising arranging the first magnet (201) and the second magnet (204) in parallel. [16] The method of claim 14, further comprising using a magnetic flux concentrator (270, 271) to increase a magnetic field of either the first magnet (201) or the second magnet (204). [17] The method of claim 16, further comprising: Inserting a first magnetic flux concentrator (270) between the first magnet (201) and the test unit table (205); and Inserting a second magnetic flux concentrator (271) between the second magnet (204) and the test unit table (205). [18] The method of claim 14, further comprising emitting light toward the device under test (2052) and applying current to the device under test (2052). [19] Data processing system (100), comprising: a processor (106); and a memory (102) storing a program which, when executed, causes the processor (106) to carry out the method for operating a rotating magnetic field measuring system according to any one of claims 14 to 18. [20] The data processing system of claim 19, wherein the processor (106) is configured to perform signal processing to extract a final Hall signal, and comprises: a signal conditioning system (1061) for data selection and background subtraction; a power spectral density analysis system (1062); and a system (1063) for lock-in detection and signal-to-noise ratio calculation.

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