A pure electric controlled nano three-dimensional magnetic sensor and its array and magnetic field measurement method

Abstract

The present invention discloses a pure electric controlled nano three-dimensional magnetic sensor and its array and magnetic field measurement method, belonging to the field of analysis and measurement control technology. The magnetic sensor includes: from bottom to top: a spin current generation layer, a magnetic material layer and an oxide layer, or from bottom to top: a spin current generation layer and a magnetic tunnel junction or a spin valve. The magnetic sensor array includes a plurality of magnetic sensors that share a spin current generation layer. The method is to apply an excitation current pulse to a single magnetic sensor, count the probability of a certain magnetization state of a bi-stable nanomagnet appearing in a random process, and calculate the component size of the magnetic field vector in the three-dimensional space direction according to the relationship between the probability and the magnetic field vector. That is, the present invention realizes the measurement of the three-dimensional magnetic field vector component in the three-dimensional space through a single nanodevice. At the same time, the magnetic sensor of the present invention is a nanodevice, which can realize nanoscale measurement, has high spatial resolution, and is small in size, and is easy to integrate on a large scale.

Description

Technical Field

[0001] The present invention belongs to the technical field of analysis and measurement control, and more specifically, relates to a purely electrically controlled nano three-dimensional magnetic sensor and its array and magnetic field measurement method. Background Art

[0002] A magnetic field sensor is a device that detects the magnitude and direction of a magnetic field and converts it into an electrical signal. It is currently widely used. A variety of sensing functions can be developed based on magnetic field sensors, including current, power, position, distance, speed, angle, etc. It has been widely used in industrial manufacturing, precision measurement, national defense and aviation, medical treatment, geography and other fields, and has a continued broad application space.

[0003] Detecting weak magnetic fields at the nanoscale has great application value in scientific research, life medicine, electronic equipment, etc. Detecting three-dimensional magnetic field vectors can obtain more and more accurate information than one-dimensional magnetic fields. Currently, nano-sized three-dimensional magnetic sensors have great application potential in application scenarios such as brain magnetometry imaging, molecular magnetic detection, material characterization, and magnetic space positioning chips.

[0004] At present, the commonly used magnetic sensors include anisotropic magnetoresistive sensors, magnetosensitive diodes, Hall sensors, fluxgate magnetometers, etc., which can detect the direction or intensity of the magnetic field, but they all have some limitations. For example, the measurement accuracy of anisotropic magnetoresistive sensors is low and requires a matching calibration algorithm; the fluxgate magnetometer is large in size and high in cost; the sensitivity of magnetosensitive diodes is low, and the signal output is only about 0.05mV / Oe, which requires matching signal amplification modules. At the same time, these magnetic sensors are large in size, and the spatial resolution of detecting magnetic fields is not high, all above microns.

[0005] Some other commonly used magnetic sensing technologies include Hall sensors, magnetic tunnel junction sensors based on tunneling magnetoresistance effect, quantum color center sensors based on nitrogen vacancies, and magnetic sensors based on superconducting quantum dot oscillators.

[0006] The Hall sensor has a simple structure and a wide measurement range. A single magnetic tunnel junction sensor can achieve sub-micron size and sufficient sensitivity. However, since a single device of these two types of magnetic sensors can only measure the magnetic field intensity in a single direction, measuring the three-dimensional magnetic field generally requires a combination of three devices, which has a more complex structure and greatly increases the size, exceeding the resolution of the nanometer size.

[0007] Although magnetic sensors based on superconducting quantum dot spectroscopy have currently achieved nanoscale magnetic detection, they can only measure one-dimensional magnetic fields. In addition, superconducting materials need to work at very low temperatures, and low-temperature facilities have greatly increased the size and complexity of the equipment.

[0008] Quantum magnetic sensors based on nitrogen vacancies sense magnetic fields through quantum color centers, and have the highest spatial resolution and extremely high sensitivity. However, they generally require complex optical and microwave equipment to assist in use, and their structures are relatively complex, making them difficult to integrate into portable devices and integrated circuit chips. In addition, since the nitrogen vacancy color centers used in the test are generally generated by irradiation at random locations, the characteristics of different devices are also random, making them unsuitable for array integration. Summary of the invention

[0009] In view of the defects and improvement needs of the prior art, the present invention provides a purely electrically controlled nano three-dimensional magnetic sensor, its array and magnetic field measurement method, the purpose of which is to realize the measurement of the three-dimensional vector of the external magnetic field with a single nanodevice.

[0010] To achieve the above-mentioned object, according to the first aspect of the present invention, a pure electrically controlled nano three-dimensional magnetic sensor is provided, which comprises, from bottom to top, a spin current generation layer, a magnetic material layer and an oxide layer; the spin current generation layer has a cross-shaped conductive channel for conducting current; the magnetic material layer is a single magnetic domain nanomagnet, which has magnetic anisotropy perpendicular to its surface under the action of the oxide layer;

[0011] Or it includes, from bottom to top, a spin current generating layer, a free layer, a tunneling layer and a fixed layer, wherein the free layer, the tunneling layer and the fixed layer constitute a magnetic tunnel junction, and the free layer is a single magnetic domain nanomagnet having magnetic anisotropy perpendicular to its surface;

[0012] Or from bottom to top, it includes: a spin current generation layer, a first magnetic layer, a non-magnetic intermediate layer, a second magnetic layer, and a pinning layer, wherein the first magnetic layer, the non-magnetic intermediate layer, the second magnetic layer, and the pinning layer constitute a spin valve. The first magnetic layer is a single magnetic domain nanomagnet with magnetic anisotropy perpendicular to its surface.

[0013] Furthermore, a protective layer is provided on the oxide layer to isolate the air.

[0014] Furthermore, the material of the spin current generating layer is a heavy metal material or a topological insulator material.

[0015] Furthermore, the material of the nanomagnet is CoFeB, CoMnSi, CoFeSi, CoFeAl, GaMnAs, CoFeAlSi, CoFe, FePt, CoPt, FeNi, Fe, Co or Ni.

[0016] Furthermore, the material of the oxide layer is MgO or Al2O3;

[0017] The material of the tunneling layer is MgO, Al2O3, AlOx, TiO2, HfO2, MgAlO4, AlN or BN;

[0018] The materials of the first magnetic layer and the second magnetic layer are CoFeB, CoMnSi, CoFeSi, CoFeAl, GaMnAs, CoFeAlSi, CoFe, FePt, CoPt, FeNi, Fe, Co or Ni;

[0019] The non-magnetic intermediate layer material is Cu, Cr, Ru or Ag;

[0020] The pinning layer material includes FeMn, IrMn, NiMn, PtMn or NiO.

[0021] According to a second aspect of the present invention, a three-dimensional magnetic field measurement method is provided, using the magnetic sensor as described in any one of the first aspects, the method comprising:

[0022] Establishing a three-dimensional rectangular coordinate system: establishing a three-dimensional rectangular coordinate system with the direction of the cross-shaped conductive channel as the x-axis and the y-axis, and the direction perpendicular to the surface of the spin current generating layer as the z-axis;

[0023] Stochastic process excitation and reading of the magnetization state of the nanomagnet: in the cross channel of the spin current generation layer, applying excitation current pulses in the positive and negative directions of the x-axis and the y-axis respectively, so that the spin current generation layer generates a spin polarized current, applies a spin-orbit torque to the nanomagnet, and then turns the magnetic moment direction of the nanomagnet to the difficult magnetization direction; removing the excitation current pulse, the magnetization state of the nanomagnet randomly returns to being perpendicular to its surface upward or downward with a certain probability under the action of the external magnetic field; applying a reading current pulse, measuring the abnormal Hall voltage at both ends of the spin current generation layer or the resistance of the magnetic tunnel junction or the resistance of the spin valve to determine the magnetization state of the nanomagnet; repeating this operation;

[0024] Calculate the probability: count the number of times a certain magnetization state occurs, and calculate the probability of the magnetization state occurring when an excitation current pulse is applied in the corresponding direction, which are recorded as P x+ , P x- , P y+ , P y- ; The probability P x+ and P x- Add them together to get the probability P1 of the magnetization state when the magnetic field is applied in the z direction. x+ and P x- Subtract the probability P2 of the magnetization state when the magnetic field is applied in the x direction. y+ and P y- Subtracting them, we get the probability P4 of the magnetization state when the magnetic field is applied in the y direction;

[0025] Calculate the magnetic field vector: Substitute the probabilities P1, P2, and P4 into the functional relationship between the probability of the magnetization state occurring and the magnetic field vector to obtain the magnitude of the external magnetic field in three directions; and obtain the magnetic field vector through vector synthesis.

[0026] Furthermore, the functional relationship between the probability of occurrence of the magnetization state and the magnetic field vector is obtained by pre-applying a detection magnetic field, comprising the following steps:

[0027] Step S1, applying excitation current pulses in the positive and negative directions of the x-axis and the positive and negative directions of the y-axis respectively;

[0028] Step S2, under each current direction, applying a detection magnetic field in the x, y, and z directions respectively;

[0029] Step S3, calculating the probability of a certain magnetization state occurring when a detection magnetic field is applied in the x, y, and z directions respectively under each current direction, and establishing a relationship between the probability and the magnitude and direction of the detection magnetic field;

[0030] Step S4: According to the relationship, a functional relationship between the probability of the magnetization state occurring and the magnetic field vector is obtained.

[0031] Furthermore, when measuring the anomalous Hall voltage, the position and direction of application of the read current pulse are the same as those of the excitation current pulse; when measuring the resistance of the magnetic tunnel junction or the resistance of the spin valve, the read current pulse is applied to the tunnel junction or the spin valve in the z-axis direction.

[0032] According to a third aspect of the present invention, there is provided a purely electrically controlled nano three-dimensional magnetic sensor array, comprising a plurality of magnetic sensors as described in any one of the first aspects, wherein the plurality of magnetic sensors share a spin current generating layer.

[0033] According to a fourth aspect of the present invention, there is provided a three-dimensional atomic force microscope scanning probe, on which a magnetic sensor as described in any one of the first aspects is integrated.

[0034] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

[0035] (1) The three-dimensional magnetic sensor of the present invention applies an excitation current pulse to the spin current generation layer to change the direction of the magnetic moment of the single magnetic domain nanomagnet, so that under the action of the external magnetic field, the magnetization state is perpendicular to its surface upward or downward with a certain probability, and the probability of a certain magnetization state of the bi-stable nanomagnet in this random process is counted, and the component size of the magnetic field vector in the three-dimensional space direction is calculated according to the relationship between the probability and the magnetic field vector. That is, the present invention realizes the measurement of the component size of the magnetic field vector in three-dimensional space through a single nanodevice. At the same time, because the magnetic sensor of the present invention is a nanodevice, it can realize nanoscale measurement, has high spatial resolution, and is small in size, and is easy to integrate on a large scale.

[0036] (2) The magnetic field measurement method of the present invention only needs to apply a current pulse to read the anomalous Hall voltage at both ends of the spin current generation layer or the resistance of the magnetic tunnel junction or the resistance of the spin valve for three different structures of magnetic sensors. The measurement is performed in a purely electrical manner without the need for complex algorithms. The measurement method is simple and does not require additional auxiliary equipment. The measurement results are accurate.

[0037] (3) Furthermore, multiple magnetic sensors are integrated on a spin current generating layer to obtain a high-density, high-spatial-resolution magnetic sensor array, which reduces the distance between magnetic sensor measurement devices to tens of nanometers and can be used for magnetic field measurement or magnetic imaging over a large spatial range.

[0038] (4) Furthermore, the magnetic sensor of the present invention is integrated into the tip of a three-dimensional atomic force microscope probe, which can realize scanning imaging of the magnetic information on the surface of the material.

[0039] In summary, the present invention realizes three-dimensional vector measurement of external magnetic field through a single device, and the device has nanometer size and nanometer spatial resolution, which expands its application potential in many fields such as chip integration, microscopic magnetic detection, magnetic imaging, magnetic positioning, molecular magnetic detection, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a schematic diagram of the first structure of the magnetic sensor proposed by the present invention.

[0041] Figure 2 This is a schematic diagram of the second structure of the magnetic sensor proposed by the present invention.

[0042] Figure 3 This is a schematic diagram of the third structure of the magnetic sensor proposed by the present invention.

[0043] Figure 4 Schematic diagram of the principle of spin-orbit torque.

[0044] Figure 5 Schematic diagram of the principle of anomalous Hall effect.

[0045] Figure 6 When the tunneling magnetoresistance effect occurs, there are two states of the magnetic tunnel junction: the left side shows the tunnel junction in a high-resistance state, and the right side shows the tunnel junction in a low-resistance state.

[0046] Figure 7 Schematic diagram of the random flipping process of the sensor.

[0047] Figure 8 This is a schematic diagram of current application during magnetic field measurement of the first magnetic sensor structure proposed by the present invention.

[0048] Fig. 9 This is a schematic diagram of current application during magnetic field measurement of the second magnetic sensor structure proposed by the present invention.

[0049] Fig.10 This is a schematic diagram of current application during magnetic field measurement of the third magnetic sensor structure proposed by the present invention.

[0050] Fig.11 Schematic diagram of the current pulse applied when the sensor measures the three-dimensional vector of the magnetic field.

[0051] Fig.12 The curves are the relationship between the probability of magnetization downward when an excitation current is applied on the x-axis and the magnitude of the magnetic field along the x, y, and z directions respectively.

[0052] Fig.13 The graphs are the relationship between the probability of magnetization downward when an excitation current is applied on the y-axis and the magnitude of the magnetic field along the x, y, and z directions, respectively.

[0053] Fig.14 The curves are the relationship between the probability of downward magnetization and the magnitude of the magnetic field along the x, y, and z directions when the sensor measures an external magnetic field in any direction.

[0054] Fig.15 This is a schematic diagram of the magnetic sensor array provided by the present invention.

[0055] Fig.16 A schematic diagram of a scanning probe of an atomic force microscope integrated with a three-dimensional magnetic sensor provided by the present invention.

[0056] Throughout the drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0057] 101 - spin current generating layer, 102 - magnetic material layer, 103 - oxide layer, 104 - protection layer, 200 - free layer, 201 - tunneling layer, 202 - fixed layer, 300 - first magnetic layer, 301 - non-magnetic intermediate layer, 302 - second magnetic layer, 303 - pinning layer. DETAILED DESCRIPTION

[0058] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0059] In the present invention, the terms "first", "second", etc. in the present invention and the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0060] For the convenience of description, in the present invention, the following is established based on the geometric characteristics of the magnetic sensor: Figure 1 , Figure 2 , Figure 3 In the three-dimensional rectangular coordinate system shown in , the direction perpendicular to the spin current generating layer 101 and from the spin current generating layer 101 to the nano-magnetic material layer is defined as the positive direction of the z-axis, and the directions of the two conductive channels of the spin current generating layer 101 are selected as the x-axis and y-axis directions respectively.

[0061] like Figure 1 As shown, the first nanometer spatial resolution three-dimensional magnetic sensor provided by the present invention is prepared by a thin film stacked with multiple layers of materials, which includes, from bottom to top: a spin current generation layer 101, a magnetic material layer 102 and an oxide layer 103;

[0062] The spin current generation layer 101 has two mutually perpendicular cross-shaped conductive channels for conducting current. Preferably, the spin current generation layer 101 is cross-shaped.

[0063] The magnetic material layer 102 is located in the center of the spin current generating layer 101. It is a single magnetic domain nanomagnet with a thickness of nanometer level. Under the action of the oxide layer 103, it has magnetic anisotropy perpendicular to the plane of the nanomagnetic material layer and has two stable magnetization states, namely, the magnetization intensity is perpendicular to the nanomagnetic material layer upward and downward.

[0064] The oxide layer 103 is used to assist the nano-magnetic material layer to obtain the magnetocrystalline anisotropy of the vertical film.

[0065] Preferably, the material of the spin current generation layer 101 is a heavy metal material such as Ta, Pt, W, Mo, Pd, Nb or a topological insulator material such as Bi2Se3, α-Sn, Sb2Te3, Bi2Te3, Bi x Sb 2-x Te3, Bi2Te2Se.

[0066] Preferably, the material of the magnetic material layer 102 may be CoFeB, CoMnSi, CoFeSi, CoFeAl, GaMnAs, CoFeAlSi, CoFe, FePt, CoPt, FeNi, Fe, Co or Ni.

[0067] Preferably, the material of the oxide layer 103 is MgO or Al2O3.

[0068] Preferably, a protective layer 104 is provided on the oxide layer 103. The material is preferably metal or oxide, which is used to isolate the air and protect the sensor to prevent the material from being oxidized.

[0069] like Figure 2 As shown, the second nanometer spatial resolution three-dimensional magnetic sensor provided by the present invention includes, from bottom to top, a spin current generation layer 101, a free layer 200, a tunneling layer 201 and a fixed layer 202, wherein the free layer, the tunneling layer and the fixed layer constitute a magnetic tunnel junction. The free layer is a nanomagnetic material, which is a nanomagnet that senses the magnetic field and has magnetic anisotropy perpendicular to its surface.

[0070] Preferably, the materials of the free layer and the fixed layer may be CoFeB, CoMnSi, CoFeSi, CoFeAl, GaMnAs, CoFeAlSi, CoFe, FePt, CoPt, FeNi, Fe, Co or Ni. The types of insulating materials used as tunneling layers include MgO, Al2O3, AlOx, TiO2, HfO2, MgAlO4, AlN or BN. Preferably, an auxiliary structure for fixing the magnetization state of the upper fixed layer, a conductive electrode made of a metal or semiconductor material or a protective layer is also provided on the magnetic tunnel junction.

[0071] like Figure 3 As shown, the third nano-spatial resolution three-dimensional magnetic sensor provided by the present invention includes, from bottom to top, a spin current generation layer 101, a first magnetic layer 300, a non-magnetic intermediate layer 301, a second magnetic layer 302, and a pinning layer 303. The first magnetic layer, the non-magnetic intermediate layer, the second magnetic layer, and the pinning layer constitute a spin valve. The first magnetic layer is a nanomagnetic material, which is a nanomagnet that senses the magnetic field and has magnetic anisotropy perpendicular to its surface.

[0072] Preferably, the materials of the first magnetic layer and the second magnetic layer may be CoFeB, CoMnSi, CoFeSi, CoFeAl, GaMnAs, CoFeAlSi, CoFe, FePt, CoPt, FeNi, Fe, Co or Ni. The non-magnetic intermediate layer material may be Cu, Cr, Ru, Ag, and the pinning layer material includes FeMn, IrMn, NiMn, PtMn, NiO.

[0073] In practical applications, the three-dimensional magnetic sensor further has a substrate layer as a support.

[0074] When measuring the external magnetic field, an excitation current pulse is applied in the positive and negative directions of the cross-shaped conductive channel of the spin current generation layer respectively, so that the spin current generation layer generates a spin polarized current, a spin orbit torque is applied to the nanomagnet, and then the magnetic moment direction of the nanomagnet is changed, and under the action of the external magnetic field, the magnetization state of the nanomagnet is made to be vertical to its surface upward or downward with a certain probability; the magnetization state of the nanomagnet is judged according to the magnitude of the anomalous Hall voltage at both ends of the spin current generation layer or the magnitude of the resistance of the magnetic tunnel junction or the magnitude of the resistance of the spin valve; the probability of a certain magnetization state occurring is counted, and the magnitude and direction of the external magnetic field are obtained according to the functional relationship between the probability and the magnetic field vector.

[0075] Specifically, Figure 4 As shown, jc represents the current density, and M represents the magnetization intensity vector of the nanomagnet (i.e., the nanomagnetic material layer or the free layer). The spin orbit torque originates from the spin Hall effect or the Rashba effect, and refers to the magnetic material structure in the spin current generation layer 101 and the adjacent spin current generation layer. When a current flows through the spin current generation layer, a spin polarized current will be generated on the upper and lower surfaces of the spin current generation layer. The spin polarized current enters the adjacent nanomagnetic material layer, which will produce a torque on the nanomagnetic material layer and change its magnetic moment direction. As shown in the figure, the magnetic moment is pulled into the plane of the nanomagnetic material layer film perpendicular to the direction of the current flowing through.

[0076] like Figure 5 As shown, for the first structure of the present invention, when current flows through the nanomagnet, a transverse voltage will be generated perpendicular to the current and the magnetization direction of the magnet. The voltage is related to the direction and magnitude of the magnetization intensity of the nanomagnet, so the magnetization state of the magnet can be judged by the voltage.

[0077] like Figure 6As shown, for the second structure of the present invention, the magnetic tunnel junction is composed of two thin layers of conductive magnetic materials (i.e., fixed layer 202 and free layer 200) and an extremely thin insulating material (tunneling layer 201) in the middle. The magnetic material of the fixed layer has a large coercive force and its magnetization is generally fixed, while the magnetization of the magnetic material of the free layer is often controlled and changed. When electrons are transferred between the free layer and the fixed layer, that is, when the current flows through the magnetic tunnel junction, they pass through the middle tunneling layer. If the magnetization directions of the fixed layer and the free layer are parallel, the scattering of the two layers with the same magnetization during tunneling is small, so the current is large and the magnetic tunnel junction is in a state of low resistance. On the contrary, if the magnetization directions of the two layers are antiparallel, the scattering of electrons when transferring from one layer to the other is large, so the current is small and in a state of high resistance. The magnetization direction of the fixed layer does not change, so the size of the resistance can be used to determine whether the magnetization of the fixed layer and the free layer is parallel or antiparallel, and then the magnetization direction of the free layer can be determined.

[0078] Similar to the second structure, for the third structure of the present invention, when the current passes through the spin valve, it will also be scattered by the magnetic layer. The difference is that the current passes through the non-magnetic intermediate layer by conduction rather than tunneling. When the magnetization direction of the first magnetic layer is parallel to the magnetization direction of the second magnetic layer, the spin valve has a smaller resistance value. When the magnetization direction of the first magnetic layer is opposite to the magnetization direction of the second magnetic layer, the spin valve has a larger resistance value, that is, the giant magnetoresistance effect. At the same time, the second magnetic layer is affected by the antiferromagnetic coupling of the pinned layer, has a higher coercive force, and the magnetization direction generally remains unchanged. Therefore, the magnetization direction of the first magnetic layer can be determined by the resistance.

[0079] In the present invention, a large current pulse is applied to a path of the cross of the spin current generation layer, which is named as the excitation current pulse and is recorded as I exc In this embodiment, I exc The current density is ~10 7 A / cm 2 . When excited by electric current, the spin current generation layer generates a sufficiently strong spin polarized current to produce a spin-orbit torque on the nanomagnetic material layer, thereby changing the direction of the magnetic moment of the nanomagnetic material layer. That is, under the action of this torque, the magnetization intensity vector of the nanomagnet is deflected from the direction perpendicular to the film (nanomagnetic material layer) to the difficult magnetization direction. Subsequently, after the excitation current is removed, the magnetization intensity state of the nanomagnet will become an unstable high-energy state. Under the influence of thermal disturbances, it will completely randomly return from the difficult magnetization direction to one of the two states perpendicular to the film upward or downward. In the absence of an external magnetic field, the probability of returning to either of these two states is equal, that is, 0.5, such as Figure 7 shown.

[0080] When there is an external magnetic field, for the first magnetic sensor structure, a small current pulse is applied to the same channel of the spin current generation layer, named as the read current pulse, denoted as I read , in this embodiment, is ~10 5 A / cm 2 The application of this current will not affect the magnetization state of the nanomagnet. The anomalous Hall voltage is measured at both ends of the spin current generation layer, such as Figure 8 As shown, the magnetization state of the nanomagnet is determined by the voltage.

[0081] For the second and third magnetic sensor structures, the state of the nanomagnet is read by applying a read current pulse I in the z direction. read , so that the current passes through the tunnel junction or spin valve from top to bottom. Due to the tunnel magnetoresistance effect or giant magnetoresistance effect, when the adjacent nanomagnets on the spin current generation layer have different magnetization directions, the corresponding resistance of the tunnel junction or spin valve formed is also different. The magnetization state of the nanomagnet on the spin current generation layer is judged by the resistance, such as Fig. 9 , Fig.10 shown.

[0082] When there is an external magnetic field, the presence of the magnetic field will cause the magnetization intensity to return to a certain state with a specific probability. In this embodiment, the probability of the magnetization direction of the nanomagnet being in the downward state is selected for testing.

[0083] This probability and the magnitude of the magnetic field conform to a specific relationship, which is obtained by pre-applying a detection magnetic field in the present invention. Fig.12 , Fig.13 As shown in the figure, the vertical axis P represents the statistical probability that the magnetization intensity of the nanomagnet is downward after the excitation current; each data point is the statistical result of multiple excitation current pulses. The horizontal axes Hx, Hy, and Hz represent the magnitude of the detection magnetic field applied along the x, y, and z axes, respectively; the gray dots in the figure represent the statistical probability that the excitation current is applied in the positive direction of the x-axis or y-axis, and the black dots represent the statistical probability that the excitation current is applied in the negative direction of the x-axis or y-axis. At the same time, it can be seen that when the magnetic field is small, the magnitude of the magnetic field and the probability are approximately linear, which is easier to use.

[0084] Specifically, in the present invention, multiple excitation current pulses are applied, and a small current pulse is applied after each excitation current pulse to perform state reading. This small current is not enough to change the magnetization state of the nanomagnet. exc and read current pulse I read Apply alternately and repeat multiple times, such as Fig.11As shown. For the first magnetic sensor structure of the present invention, the anomalous Hall effect is generated, and the magnetization state is determined by the level of the anomalous Hall voltage; for the second and third magnetic sensor structures of the present invention, the tunneling magnetoresistance effect or giant magnetoresistance effect is generated by passing the current from top to bottom through the tunnel junction or spin valve, and the magnetization state of the nanomagnet on the spin current generation layer is determined by the resistance of the tunnel junction or spin valve.

[0085] The probability of a certain state occurring is calculated by a comparator counter and other circuits. In this embodiment, the probability of the magnetization downward state of the nanomagnet is calculated, and the relationship between the probability of a certain magnetization state occurring and the components of the magnetic field vector in three directions is obtained according to the probability size, the detection magnetic field size and the direction. Preferably, the probability and the size of the detection magnetic field satisfy the Sigmoid function relationship, and the relationship between the probability of a certain magnetization state occurring and the components of the magnetic field vector in three directions can be obtained by the probability size, the detection magnetic field size, and the probability and the size of the detection magnetic field satisfying the Sigmoid function relationship.

[0086] When measuring the three-dimensional magnetic field vector in any direction, the magnetic field vector can be regarded as the superposition of the magnetic field vectors along the x, y, and z directions, and its effect on probability will also produce superposition. Fig.12 , Fig.13 It can be seen that when the excitation current is applied to the positive and negative directions of the x-axis respectively, the effect of applying a magnetic field in the x-direction on the probability, that is, the law of the change of probability, is that the two have the characteristics of equal magnitude and opposite direction. The change of probability caused by applying a magnetic field in the z-direction is the same, while applying a magnetic field in the y-direction has no effect on the probability. Therefore, when Hx, Hy, and Hz exist at the same time, the magnetic field applied in the x-direction can be offset by applying an excitation current in the positive and negative directions of the x-axis at the same time. The sum of probabilities obtained is only related to the magnetic field applied in the z-direction, and the probability P1 of a certain magnetization state is equivalent to that when the magnetic field is applied in the z-direction; subtracting the probabilities can offset the magnetic field applied in the z-direction, and the probability difference obtained is only related to the magnetic field applied in the x-direction, and the probability P2 of a certain magnetization state is equivalent to that when the magnetic field is applied in the x-direction.

[0087] Similarly, applying excitation current in the positive and negative directions of y respectively and adding the probabilities can offset the effect of the magnetic field applied in the y direction. The obtained probability sum is only related to the magnetic field applied in the z direction, and the probability P3 of a certain magnetization state is equivalent to the magnetic field applied in the z direction; subtracting the probabilities can offset the effect of the magnetic field applied in the z direction. The obtained probability sum is only related to the magnetic field applied in the y direction, and the probability P4 of a certain magnetization state is equivalent to the magnetic field applied in the y direction. Thereby, the function of measuring any magnetic field vector is realized. Substituting the probabilities P1, P2, and P4 into the above functional relationship obtained according to the detection magnetic field, the sizes of the three components of any magnetic field are obtained, and the magnetic field vector is obtained through vector synthesis, such as Fig.14 shown.

[0088] Specifically, the three-dimensional magnetic field measurement method of the present invention comprises the following steps:

[0089] Stochastic process excitation and reading of the magnetization state of the nanomagnet: In the cross channel of the spin current generation layer, a large current pulse is applied to the positive and negative directions of the x-axis and the y-axis respectively. Here, we name this current as an excitation current pulse. The excitation current pulse causes the spin current generation layer to generate a spin polarized current, applies a spin-orbit torque to the nanomagnet, and then changes the magnetic moment direction of the nanomagnet to a difficult magnetization direction. After the excitation current pulse is removed, under the action of the external magnetic field, the magnetization state of the nanomagnet randomly returns to being perpendicular to its surface upward or downward with a certain probability; then a smaller current pulse is applied, which we name as a reading current pulse, and the anomalous Hall voltage at both ends of the spin current generation layer or the resistance of the magnetic tunnel junction or the resistance of the spin valve is measured to determine the magnetization state of the nanomagnet; the random process excitation and reading of the magnetization state of the nanomagnet are repeated;

[0090] Calculate the probability: count the number of times a certain magnetization state occurs, and calculate the probability of the magnetization state occurring when an excitation current pulse is applied in the corresponding direction, which are recorded as P x+ , P x- , P y+ , P y- ; The probability P x+ and P x- Add them together to get the probability P1 of the magnetization state when the magnetic field is applied in the z direction. x+ and P x- Subtract the probability P2 of the magnetization state when the magnetic field is applied in the x direction. y+ and P y- Add them together to get the probability P3 of the magnetization state when the magnetic field is applied in the z direction. y+ and P y-Subtract them to obtain the probability P4 of the magnetization state when the magnetic field is applied in the y direction. In this embodiment, P1=(P x+ +P x- ) / 2, P2=P x+ -P x- , P3=(P y+ +P y- ) / 2, P4=P y+ -P y- At the same time, it can be seen that P1 and P3 both represent the probability of the magnetization state when the magnetic field is applied in the z direction, P1 = P3.

[0091] Calculate the magnetic field vector: Substitute the probabilities P1, P2, and P4 into the functional relationship between the probability of the magnetization state and the magnetic field vector to obtain the magnitude of the external magnetic field in three directions; obtain the magnetic field vector through vector synthesis, such as Fig.14 shown.

[0092] The functional relationship between the probability of the magnetization state occurring and the magnetic field vector is obtained by applying a detection magnetic field in advance, and includes the following steps:

[0093] Step S1, applying excitation current pulses in the positive and negative directions of the x-axis and the positive and negative directions of the y-axis respectively;

[0094] Step S2, under each current direction, applying a detection magnetic field in the x, y, and z directions respectively;

[0095] Step S3, calculating the probability of a certain magnetization state occurring when a detection magnetic field is applied in the x, y, and z directions respectively under each current direction, and establishing a relationship between the probability and the magnitude and direction of the detection magnetic field;

[0096] Step S4: According to the relationship, a functional relationship between the probability of the magnetization state occurring and the magnetic field vector is obtained.

[0097] like Fig.15 As shown, based on the magnetic sensor provided above, the present invention also provides an array-type magnetic sensor, which is composed of a plurality of the above-mentioned magnetic sensors. The array-type magnetic sensor is composed of a plurality of the above-mentioned magnetic sensors sharing a spin current generation layer, and all the magnetic sensors can be driven simultaneously by applying an excitation current, thereby accelerating the average operating speed of a large number of devices in the array.

[0098] like Fig.16As shown, based on the magnetic sensor provided above, the present invention also provides a three-dimensional scanning probe, by setting the magnetic sensor at the tip of an atomic force microscope probe or other probes, the closer the magnetic sensor is to the sample, the stronger the magnetic field, the more accurate the detection, and the finer the detectable details and resolved structures. With the help of an atomic force microscope, the sensor is placed close to the sample surface, and the surface magnetic field is measured while measuring the material surface morphology. The magnetic information of the sample surface is plotted in this way of the present invention, with higher accuracy and flexibility.

[0099] The magnetic sensor of the present invention is a nanometer-level device. Existing industrial practice has proved that the size can be as small as 30 nanometers. Moreover, it is theoretically predicted that the size can be further reduced to about 10 nanometers through improvements in material technology. Therefore, the magnetic field sensor can achieve a very small size, thereby achieving ultra-high spatial resolution, expanding its application potential in many fields such as chip integration, microscopic magnetic detection, magnetic imaging, magnetic positioning, molecular magnetic detection, etc.

[0100] The present invention is based on the working mode of spin correlation effect (spin-orbit torque, anomalous Hall effect, tunneling magnetoresistance effect, giant magnetoresistance effect), and the single current pulse time can reach nanoseconds, which can perform high-speed measurement. And the more times the operation of judging the magnetization state of the nanomagnet is, the more accurate the probability obtained by statistics is, and the more accurate the magnetic field vector result obtained is. At the same time, the method of the present invention performs magnetic field vector measurement at room temperature, which solves the technical problem that the prior art needs to be measured at very low temperatures.

[0101] The structure and process of the magnetic sensor of the present invention are relatively simple. By sharing the spin current generation layer, a high-density sensor array can be easily prepared. The spacing between devices is reduced to tens of nanometers, which can be used for magnetic field measurement or magnetic imaging in a large spatial range. It can also be integrated into the probe tip of an atomic force microscope to scan the magnetic information on the surface of the material.

[0102] Through a single magnetic sensor, the three spatial components of the three-dimensional magnetic field vector can be measured, which reduces the number and complexity of devices for measuring the magnetic field vector compared to the existing technology.

[0103] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for measuring three-dimensional magnetic field using a purely electrically controlled nano three-dimensional magnetic sensor, characterized in that: The purely electrically controlled nano three-dimensional magnetic sensor comprises, from bottom to top, a spin current generation layer (101), a magnetic material layer (102) and an oxide layer (103); the spin current generation layer (101) has a cross-shaped conductive channel for conducting current; the magnetic material layer (102) is a single magnetic domain nanomagnet, and has magnetic anisotropy perpendicular to its surface under the action of the oxide layer (103); Or it comprises, from bottom to top, a spin current generating layer (101), a free layer (200), a tunneling layer (201) and a fixed layer (202), wherein the free layer (200), the tunneling layer (201) and the fixed layer (202) constitute a magnetic tunnel junction, and the free layer is a single magnetic domain nanomagnet having magnetic anisotropy perpendicular to its surface; Or the invention comprises, from bottom to top, a spin current generating layer (101), a first magnetic layer (300), a non-magnetic intermediate layer (301), a second magnetic layer (302), and a pinning layer (303), wherein the first magnetic layer (300), the non-magnetic intermediate layer (301), the second magnetic layer (302), and the pinning layer (303) constitute a spin valve, and the first magnetic layer is a single magnetic domain nanomagnet having magnetic anisotropy perpendicular to its surface; the three-dimensional magnetic field measurement method is: Establishing a three-dimensional rectangular coordinate system: establishing a three-dimensional rectangular coordinate system with the direction of the cross-shaped conductive channel as the x-axis and the y-axis, and the direction perpendicular to the surface of the spin current generating layer as the z-axis; Stochastic process excitation and reading of the magnetization state of the nanomagnet: in the cross channel of the spin current generation layer, applying excitation current pulses in the positive and negative directions of the x-axis and the y-axis respectively, so that the spin current generation layer generates a spin polarized current, and applies a spin-orbit torque to the nanomagnet, thereby turning the magnetic moment direction of the nanomagnet to the difficult magnetization direction; removing the excitation current pulse, the magnetization state of the nanomagnet randomly returns to being perpendicular to its surface upward or downward with a certain probability under the action of the external magnetic field; applying a read current pulse, measuring the abnormal Hall voltage at both ends of the spin current generation layer or the resistance of the magnetic tunnel junction or the resistance of the spin valve to determine the magnetization state of the nanomagnet; repeating this operation; Calculate the probability: count the number of times a certain magnetization state occurs, and calculate the probability of the magnetization state occurring when an excitation current pulse is applied in the corresponding direction, which are recorded as P x+ , P x- , P y+ , P y- ; The probability P x+ and P x- Add them together to get the probability P1 of the magnetization state when the magnetic field is applied in the z direction. x+ and P x- Subtract the probability P2 of the magnetization state when the magnetic field is applied in the x direction. y+ and P y- Subtracting them, we get the probability P4 of the magnetization state when the magnetic field is applied in the y direction; Calculate the magnetic field vector: Substitute the probabilities P1, P2, and P4 into the functional relationship between the probability of the magnetization state occurring and the magnetic field vector to obtain the magnitude of the external magnetic field in three directions; and obtain the magnetic field vector through vector synthesis.

2. The three-dimensional magnetic field measurement method according to claim 1, characterized in that: The functional relationship between the probability of occurrence of the magnetization state and the magnetic field vector is obtained by pre-applying a detection magnetic field, and includes the following steps: Step S1, applying excitation current pulses in the positive and negative directions of the x-axis and the positive and negative directions of the y-axis respectively; Step S2, applying a detection magnetic field in the x, y, and z directions respectively under each current direction; Step S3, calculating the probability of a certain magnetization state occurring when a detection magnetic field is applied in the x, y, and z directions respectively under each current direction, and establishing a relationship between the probability and the magnitude and direction of the detection magnetic field; Step S4: According to the relationship, a functional relationship between the probability of the magnetization state occurring and the magnetic field vector is obtained.

3. The three-dimensional magnetic field measurement method according to claim 2, characterized in that: When measuring the anomalous Hall voltage, the position and direction of application of the read current pulse are the same as those of the excitation current pulse; when measuring the resistance of the magnetic tunnel junction or the resistance of the spin valve, the read current pulse is applied to the tunnel junction or the spin valve in the z-axis direction.

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