A magnetic sensor based on bulk acoustic wave spin pumping effect

Abstract

The application discloses a kind of magnetic sensors based on bulk acoustic wave spin pumping effect, belong to magnetic sensor technical field.The application includes bulk acoustic wave transducer and spin pumping structure, the bulk acoustic wave is output after the bulk acoustic wave transducer starts, the bulk acoustic wave excites the spin pumping structure under the magnetic field to be measured and exports magnetic sub-flow, the magnetic sub-flow generates inverse spin hall voltage by inverse spin hall effect, and the magnetic field intensity to be measured and direction are derived by the change of the inverse spin hall voltage;The magnetic sensor disclosed in the application has high sensitivity, low power consumption and the advantages such as easy integration, and has wide application prospect in magnetic sensor technology.

Description

Technical Field

[0001] This invention belongs to the field of magnetic sensor technology, and more specifically, relates to a magnetic sensor based on the spin pumping effect of bulk acoustic waves. Background Technology

[0002] Magnetic sensors are used to measure the strength or change of a magnetic field. They have wide applications in industry, medicine, aerospace, automotive, and electronics. For example, magnetic sensors can be used to measure mechanical motion, detect the Earth's magnetic field, detect current, measure liquid level, and detect metals. Common types of magnetic sensors include Hall effect sensors, magnetoresistive sensors, inductive sensors, and magnetoelectric sensors. Each has its own advantages and disadvantages, and different types of magnetic sensors can be selected according to different application requirements. Compared with traditional magnetic sensors, spin magnetic sensors have advantages such as high sensitivity, high resolution, fast response speed, good temperature stability, and non-contact measurement.

[0003] Common types of spin magnetic sensors include giant magnetoresistive spin sensors, tunneling magnetoresistive spin sensors, spin Hall effect sensors, and magnetoresistive spin sensors. Spin-pumped magnetic sensors can utilize the spin pumping effect to convert non-equilibrium spins into voltage signals, achieving highly sensitive magnetic field measurements. Common spin pumping techniques include ferromagnetic resonance spin pumping and pulsed laser spin pumping. Ferroresonance-based spin pumping has high power consumption, large transmission damping, and low excitation efficiency of the magnetic subfluid. Pulsed laser spin pumping, on the other hand, requires extremely precise pulse widths, is complex to operate, and is limited by available materials. Summary of the Invention

[0004] In view of the above-mentioned defects or improvement needs of the existing technology, the present invention provides a magnetic sensor based on the spin pumping effect of bulk acoustic waves, which aims to solve the technical problems of high power consumption, low efficiency, complex operation and limited materials of existing spin magnetic sensors.

[0005] To achieve the above objectives, the present invention provides a magnetic sensor based on the bulk acoustic wave spin pumping effect. The magnetic sensor includes a bulk acoustic wave transducer and a spin pumping structure. After the bulk acoustic wave transducer is activated, it outputs a bulk acoustic wave. The bulk acoustic wave excites the spin pumping structure to output a magnetic wave flux under the magnetic field to be measured. The magnetic wave flux generates an inverse spin Hall voltage through the inverse spin Hall effect. The strength and direction of the magnetic field to be measured are derived from the inverse spin Hall voltage.

[0006] Preferably, the bulk acoustic transducer includes a lower electrode layer, a piezoelectric layer, and an upper electrode layer, with the piezoelectric layer located between the lower electrode layer and the upper electrode layer; when a voltage is applied to the lower electrode layer and the upper electrode layer, strain resonance will be generated in the piezoelectric layer, thereby outputting a bulk acoustic wave;

[0007] The spin pumping structure includes a ferromagnetic layer and a non-magnetic conductor layer; the ferromagnetic layer is located close to the bulk acoustic transducer; the ferromagnetic layer outputs a magnetic flux under the combined action of the acoustic bulk wave and the magnetic field to be measured, and the magnetic flux generates an inverse spin Hall voltage in the non-magnetic conductor layer through the inverse spin Hall effect.

[0008] Preferably, the lower electrode layer and the upper electrode layer are made of metal electrode materials; the piezoelectric layer is made of piezoelectric thin film material; the ferromagnetic layer is made of ferromagnetic insulator material; and the non-magnetic conductor layer is made of metal electrode material.

[0009] Preferably, the materials used for the lower electrode layer and the upper electrode layer include, but are not limited to, Pt, Cu, Ag, Zn, Al, Li, Mo, W, Ti, Cr, Nb, Ru, Rh, Pd, Hf, Ta, Re, Ir, or Au.

[0010] Preferably, the piezoelectric layer is made of materials including, but not limited to, AlN, ZnO, and Pb(Zr). x Ti 1-x O3 or Al 1- x Sc x N.

[0011] Preferably, the ferromagnetic layer is made of materials including, but not limited to, Y3Fe5O. 12 CoFe2O4 or NiFe2O4.

[0012] Preferably, the non-magnetic conductor layer is made of materials including but not limited to Pt, Cu, Ag, Zn, Al, Li, Mo, W, Ti, Cr, Nb, Ru, Rh, Pd, Hf, Ta, Re, Ir, or Au.

[0013] Preferably, the materials of the lower electrode layer and the upper electrode layer are Al; the material of the piezoelectric layer is Al. 0.93 Sc 0.07 N; the material of the ferromagnetic layer is CoFe2O4; the material of the non-magnetic conductor layer is Pt;

[0014] Preferably, the relationship between the direction of the magnetic field to be measured and the inverse spin Hall voltage is as follows:

[0015]

[0016] The root mean square error is 0.0238; among which, Indicates the inverse spin Hall voltage; This represents the angle between the direction of the magnetic field being measured and the direction of propagation of the bulk sound wave. Based on the above equation, the inverse spin Hall voltage Determine the direction of the magnetic field to be measured .

[0017] Preferably, the magnetic field strength to be measured and inverse spin Hall voltage The relationship is:

[0018] When the measurement range of the magnetic field strength to be measured is 0.01T to 0.25T:

[0019]

[0020] The root mean square error is 0.1008;

[0021] When the measurement range of the magnetic field strength to be measured is 0.08T to 0.20T:

[0022]

[0023] The root mean square error is 0.0203;

[0024] Based on the above two equations, the inverse spin Hall voltage Determine the strength of the magnetic field to be measured .

[0025] In summary, the technical solutions conceived by this invention have the following beneficial effects compared with the prior art:

[0026] (1) The present invention realizes a new magnetic sensor structure. By measuring the inverse spin Hall voltage output by the structure, the direction and intensity of the magnetic field to be measured can be sensed. Compared with other magnetic sensors, the magnetic sensor of the present invention does not need to provide an additional magnetic field. It can directly use the magnetic field to be measured to realize the ferromagnetic layer magnetic particle flow pump, thereby realizing magnetic field measurement and reducing the complexity of magnetic field measurement.

[0027] (2) This invention is based on the spin pumping effect of bulk acoustic waves and uses the interaction between bulk acoustic waves and magnetic fields to achieve magnetic field measurement. Compared with traditional acoustic spin pumping, it has higher sensitivity.

[0028] (3) Based on the bulk acoustic wave spin pumping effect, the present invention can achieve high resolution and detect minute magnetic field changes; at the same time, the bulk acoustic wave spin pumping has a fast response speed and can realize high-speed magnetic field measurement.

[0029] (4) Based on the spin pumping effect of bulk acoustic waves, the present invention has good temperature stability and can work in a wide temperature range; at the same time, it can realize non-contact magnetic field measurement, which can expand the application scenarios of the sensor. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the magnetic sensor structure in an embodiment of the present invention;

[0031] Figure 2This is a schematic diagram of the bulk acoustic wave transducer structure in an embodiment of the present invention;

[0032] Figure 3 This is a schematic diagram of the spin pump structure in an embodiment of the present invention;

[0033] Figure 4 This is a simulation result diagram of magnetic field direction sensing in an embodiment of the present invention;

[0034] Figure 5 This is a simulation result diagram of magnetic field strength sensing in an embodiment of the present invention;

[0035] Figure 6 This is a simulation result diagram of the magnetic field strength sensing with a reduced measurement range in an embodiment of the present invention;

[0036] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1 is the upper electrode layer, 2 is the piezoelectric layer, 3 is the lower electrode layer, 4 is the ferromagnetic insulator layer, and 5 is the non-magnetic conductor layer. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0038] This invention provides a magnetic sensor based on the spin pumping effect and the inverse spin Hall effect. It uses a bulk acoustic transducer as the excitation source of the spin pumping structure and utilizes the inverse spin Hall voltage generated by the inverse spin Hall effect to respond to the direction and intensity of the applied magnetic field, thereby achieving efficient, energy-saving and highly sensitive magnetic field sensing.

[0039] The magnetic sensor of the present invention includes a bottom-up spin pump structure and an acoustic bulk wave transducer structure. After the acoustic bulk wave transducer is activated by voltage, its output bulk acoustic wave excites the spin pump structure to output a magneton current under the magnetic field to be measured. The magneton current is converted into an inverse spin Hall voltage through the inverse spin Hall effect. This voltage changes with the strength and direction of the magnetic field to be measured, so as to achieve the purpose of magnetic field sensing.

[0040] like Figure 1As shown, the ferromagnetic insulator layer 4 is in contact with the lower electrode 3 of the bulk acoustic wave transducer. The stress transmitted by the bulk acoustic wave output from the bulk acoustic wave transducer changes the structural strain of the ferromagnetic insulator layer 4, thereby changing the state of the magnetic domains inside the ferromagnetic insulator layer 4 and causing magnetic moment precession. The periodically changing bulk acoustic wave causes the magnetic domains of the ferromagnetic insulator layer 4 to undergo periodic flipping, thereby continuously pumping the magnetic flux to the non-magnetic conductor layer 5. The magnetic flux is converted into an inverse spin Hall current in the non-magnetic conductor layer 5 through the inverse spin Hall effect. The inverse spin Hall current causes a potential difference, i.e., an inverse spin Hall voltage, to appear on both sides of the non-magnetic conductor layer 5 due to charge accumulation. The sensing of magnetic field strength and direction can be achieved by measuring the change of the spin Hall voltage when the magnetic field strength and direction change.

[0041] like Figure 1 , 2 As shown in Figure 3, the magnetic sensor of the present invention includes a bulk acoustic transducer and a spin pump structure. The bulk acoustic transducer consists of an upper electrode 1, a piezoelectric layer 2, and a lower electrode 3 from top to bottom. The spin pump structure consists of a ferromagnetic insulator layer 4 and a non-magnetic conductor layer 5 from top to bottom.

[0042] By structurally designing the bulk acoustic transducer, the output bulk acoustic frequency can be adjusted, thereby selecting a bulk acoustic frequency that is more compatible with the spin pump structure, thus improving the magnetoelastic coupling effect strength and enhancing the test sensitivity of the magnetic sensor.

[0043] In this embodiment, the upper electrode 1 and lower electrode 3 of the bulk acoustic transducer are specifically Al. In other examples, the upper electrode 1 and lower electrode 3 of the bulk acoustic transducer may also be, but are not limited to, Pt, Cu, Ag, Zn, Li, Mo, W, Ti, Cr, Nb, Ru, Rh, Pd, Hf, Ta, Re, Ir, or Au.

[0044] In this embodiment, the upper electrode 1 and lower electrode 3 of the bulk acoustic transducer have a specific thickness of 0.28 μm. In other examples, the thickness of the upper and lower electrodes can also be 0.1~1.0 μm.

[0045] In this embodiment, the upper electrode 1 and lower electrode 3 of the bulk acoustic transducer are specifically fabricated by magnetron sputtering. In other examples, the thickness of the upper and lower electrodes can also be achieved by electron beam evaporation (E... Prepared by methods such as beam (beam) and thermal evaporation.

[0046] In this embodiment, the piezoelectric layer 2 in the bulk acoustic transducer is specifically Al. 0.93 Sc 0.07 N. In other instances, the piezoelectric layer 2 of the bulk acoustic transducer may also be, but is not limited to, ZnO, AlN, Al 1-x Sc x N or Pb(Zr)x Ti 1-x )O3.

[0047] In this embodiment, the piezoelectric layer 2 in the bulk acoustic transducer has a specific thickness of 2 μm. In other examples, the thickness of the piezoelectric layer 2 can also be 1~10 μm.

[0048] In this embodiment, the piezoelectric layer 2 in the bulk acoustic transducer is specifically prepared by reactive magnetron sputtering. In other examples, the thickness of the piezoelectric layer 2 can also be prepared by chemical vapor deposition, molecular beam epitaxy, and pulsed laser methods.

[0049] In this embodiment, the spin-pumped ferromagnetic insulator layer 4 is specifically CoFe2O4. In other examples, the ferromagnetic insulator layer 4 may also be, but is not limited to, Y3Fe5O4. 12 And NiFe2O4.

[0050] In this embodiment, the thickness of the ferromagnetic insulator layer 4 in the spin-pumped structure is specifically 8.8 μm. In other examples, the thickness of the ferromagnetic insulator layer 4 can also be 1~100 μm.

[0051] In this embodiment, the spin-pumped ferromagnetic insulator layer 4 is specifically prepared by pulsed laser deposition. In other examples, the ferromagnetic insulator layer 4 can also be prepared by methods including but not limited to reactive magnetron sputtering, chemical vapor deposition, and molecular beam epitaxy.

[0052] In this embodiment, the non-magnetic conductor layer 5 of the spin-pumped structure is specifically Pt. In other examples, the non-magnetic conductor layer 5 may also be, but is not limited to, Al, Cu, Ag, Zn, Li, Mo, W, Ti, Cr, Nb, Ru, Rh, Pd, Hf, Ta, Re, Ir, or Au.

[0053] In this embodiment, the thickness of the non-magnetic conductor layer 5 in the spin pump structure is specifically 4 μm. In other examples, the thickness of the non-magnetic conductor layer 5 can also be 0.1~10 μm.

[0054] In this embodiment, the non-magnetic conductor layer 5 of the spin-pumped structure is specifically prepared by magnetron sputtering deposition. In other examples, the thickness of the non-magnetic conductor layer 5 can also be prepared by methods including but not limited to pulsed laser deposition, chemical vapor deposition, and molecular beam epitaxy.

[0055] When the direction of the magnetic field being measured changes from 0° to 180° with the direction of bulk acoustic wave propagation, the magnitude of the inverse spin Hall voltage varies with the direction of the magnetic field, and the two have a cubic relationship, as shown in the figure. Figure 4 As shown, the expression for the cubic fitting curve is:

[0056]

[0057] The root mean square error of the fit was 0.0238.

[0058] When the strength of the magnetic field to be measured changes from 0.01 to 0.25 T, the magnitude of the inverse spin Hall voltage varies with the magnetic field strength, and the two are linearly correlated, such as... Figure 5 As shown, the linear fitting expression is:

[0059]

[0060] The root mean square error is 0.1008;

[0061] When the measurement range of the magnetic field strength to be measured is reduced to 0.08–0.20 T, such as Figure 6 As shown, the linear fitting expression is:

[0062]

[0063] The root mean square error is 0.0203.

[0064] In summary, this example can form a magnetic sensor. By generating high-frequency acoustic bulk waves through a bulk acoustic transducer to excite a spin-pumped structure, the strength and direction of the magnetic field to be measured will affect the magnetoelastic coupling effect of phonons and magnetons in the ferromagnetic insulating layer of the spin-pumped structure, thereby affecting the magnitude of the output magneton current. This, in turn, changes the magnitude of the inverse spin Hall voltage in the non-magnetic conductor layer of the spin-pumped structure, thus realizing magnetic sensing and forming a prototype of a high-efficiency, low-power, and high-sensitivity magnetic sensor with practical application value.

[0065] In addition to the specific materials and structures used in the above embodiments, other materials, acoustic wave generator structures, and spin pump structures with similar effects can also be used.

[0066] The above content is readily understood by those skilled in the art. The above description is merely 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 within the protection scope of the present invention.

Claims

1. A magnetic sensor based on the spin-pumping effect of bulk acoustic waves, characterized in that, The magnetic sensor includes a bulk acoustic wave transducer and a spin pumping structure. After activation, the bulk acoustic wave transducer outputs a bulk acoustic wave. Under the magnetic field to be measured, the bulk acoustic wave excites the spin pumping structure to output a magnetic wave flux. This magnetic wave flux generates an inverse spin Hall voltage through the inverse spin Hall effect. The strength and direction of the magnetic field to be measured are derived from this inverse spin Hall voltage. Specifically: By fitting example data, it was found that the inverse spin Hall voltage and the direction of the magnetic field to be measured form a cubic curve relationship, and the inverse spin Hall voltage and the strength of the magnetic field to be measured have a linear correlation relationship. The bulk acoustic transducer includes a lower electrode layer, a piezoelectric layer, and an upper electrode layer, with the piezoelectric layer located between the lower electrode layer and the upper electrode layer. When a voltage is applied to the lower electrode layer and the upper electrode layer, strain resonance will be generated in the piezoelectric layer, thereby outputting a bulk acoustic wave. The spin pumping structure includes a ferromagnetic layer and a non-magnetic conductor layer; the ferromagnetic layer is close to the bulk acoustic transducer; the ferromagnetic layer outputs a magnetic flux under the combined action of the acoustic bulk wave and the magnetic field to be measured, and the magnetic flux generates an inverse spin Hall voltage in the non-magnetic conductor layer through the inverse spin Hall effect; The lower and upper electrode layers are made of Al; the piezoelectric layer is made of Al. 0.93 Sc 0.07 N; the material of the ferromagnetic layer is CoFe2O4; the material of the non-magnetic conductor layer is Pt.

2. The magnetic sensor according to claim 1, characterized in that, The lower and upper electrode layers are made of metal electrode materials; the piezoelectric layer is made of piezoelectric thin film material; the ferromagnetic layer is made of ferromagnetic insulator material; and the non-magnetic conductor layer is made of metal electrode material.

Images