MR sensor with layer orientation control using SOT current

Abstract

A method and apparatus for an MR device having a ferromagnetic material, a heavy metal layer configured to conduct a charge current, and an insulating layer between the ferromagnetic material and the heavy metal layer. The insulating layer is configured to electrically insulate and magnetically couple the heavy metal layer and the ferromagnetic layer in order to generate a field-like (FL) magnetic field within the ferromagnetic material in response to the charge current. In some embodiments, the MR device comprises a TMR device having a free layer or reference layer oriented by the charge current. In other embodiments, the MR device comprises a GMR device.

Description

[Background technology]

[0001]

[0001] Magnetic field sensors are used in a variety of applications, including, but not limited to, angle detection for detecting the angle of the direction of a magnetic field, current detection for detecting a magnetic field generated by an electric current carried by an electric conductor, magnetic switching for detecting the proximity of a ferromagnetic object, rotation detection for detecting magnetic domains of a passing ferromagnetic article, such as a ring magnet or ferromagnetic target (e.g., the teeth of a gear) (magnetic field sensors are used in combination with a reverse-biased magnet or other magnets), and magnetic field detection for detecting the magnetic field density of a magnetic field.

[0002]

[0002] In certain applications, magnetic field sensors include magnetoresistive elements. These elements have an electrical resistance that changes in the presence of an external magnetic field. A spin valve is a type of magnetoresistive element formed from two or more magnetic materials or layers. The simplest form of a spin valve has a reference (or magnetically fixed) layer and a free layer. The resistance of a spin valve changes as a function of the magnetization arrangement of the reference and free layers. Typically, the magnetization arrangement of the reference layer does not change, but the magnetization arrangement of the free layer moves in response to an external magnetic field. When the separation between the free layer and the reference layer is a thin insulating layer, the spin valve is called a TMR spin valve.

[0003]

[0003] In some cases, spin valves may also have a bias. A bias may be generated by one or more magnetic layers (bias layers) that are magnetically coupled to the free layer. In the absence of an external magnetic field, the bias layers may cause the magnetization of the free layer to return to a predetermined arrangement. Because the magnetic coupling between the bias layer and the free layer is relatively weak, an external magnetic field can release the bias and rearrange the magnetization of the free layer. [Overview of the Initiative]

[0004]

[0004] Embodiments of the present disclosure provide methods and apparatus for controlling the free layer and / or reference layer of a sensor for an MR sensor having a tuned spin-orbit torque (SOT). A charge current can be injected through a heavy metal (HM) layer in contact with the ferromagnetic layer to generate a spin current used to control the magnetic orientation of the ferromagnetic layer within the sensor. The HM layer may be in direct contact with the ferromagnetic layer without electrical insulation. Simultaneous execution of SOT control of the ferromagnetic layer and TMR reading operation can be achieved by a floating power supply used with an HM shared by two TMR pillars. The SOT may be used to switch the reference in a stable orientation state without simultaneous TMR reading in an architecture using switches to allow TMR pillars to be connected in series. In embodiments, the sensor includes a laminated structure having an insulating layer that allows simultaneous control of the ferromagnetic layer while reading TMR pillars connected in series. In this embodiment, the insulating layer provides electrical insulation between the ferromagnetic layer and the heavy metal, so that the current flows through a tunnel barrier of pillars connected in series, rather than through the insulating material to the heavy metal. The insulating layer also enables field-like (FL) or damping-like (DL) transmission generated by the spin current, due to its good conductivity for spin Hall currents and / or by Rashba coupling.

[0005]

[0005] In some embodiments, the HM is magnetically connected to the free layer, so that the laminated structure allows control of the free layer. A charge current parallel to the reference magnetic orientation (sensitivity axis) may generate an FL magnetic field that biases the free layer perpendicular to the sensitivity axis: this linearizes the response of the laminate - the laminated linear range can be dynamically modulated by changing the charge current (i.e., the FL magnetic field). A charge current perpendicular to the reference magnetic orientation generates an FL magnetic field along the sensitivity axis: this FL magnetic field can be used to cancel out the magnetic field in a feedback loop architecture (replacing an external coil). In some embodiments, charge currents having parallel and perpendicular components are used simultaneously to linearize the laminate and cancel out the magnetic field.

[0006]

[0006] In some embodiments, the MR sensor includes metal contacts between free layers to allow for individual sizing of the free layers. In some embodiments, the MR sensor has a laminated structure for oriented the reference layer. The charge current direction along the reference axis can be varied at high frequencies: the reference magnetic orientation can be switched at high frequencies to chop up removeable electron 1 / f noise and offset. In some embodiments, a charge current having two components can be used to set the reference in any direction (0 to 360 degrees) to realize certain sensors such as angle sensors.

[0007]

[0007] In the embodiment, the GMR sensor includes SOT adjustment for controlling the ferromagnetic layer without reducing magnetoresistance.

[0008]

[0008] Not only the present invention itself, but also the aforementioned features of the present invention can be understood more completely from the following description in the drawings. [Brief explanation of the drawing]

[0009] [Figure 1]

[0009] This is a schematic diagram of an exemplary sensor having an MR element with SOT adjustment. [Figure 2]

[0010] This is a schematic diagram of an MR bridge including an MR element. [Figure 3]

[0011] This is a schematic diagram of a bridge resistor having a TMR pillar with SOT adjustment. [Figure 4]

[0012] This is a schematic diagram of an MTJ including tunnel magnetoresistance. [Figure 5]

[0013] This is a schematic diagram of field-like orientation and damping-like orientation as a function of current and magnetization orientation in a thin magnetic film in contact with an HM film. [Figure 6]

[0014] FIG. 6A is a schematic diagram of a spin valve having ferromagnetic layers separated by a spacer layer, FIG. 6B is a diagram showing a spin valve having ferromagnetic layers separated by a spacer layer and an antiferromagnetic layer for orienting a reference layer, and FIG. 6C is a diagram showing a spin valve having ferromagnetic layers separated by a spacer layer, an antiferromagnetic layer for orienting a reference layer, and a synthetic antiferromagnet (SAF) layer for orienting the reference layer. [Figure 7]

[0015] FIG. 7A is a diagram showing a charge current flowing into the page and a resulting spin current flowing to the reference layer including an in-plane FL magnetic field for orienting the reference layer, and FIG. 7B is a diagram showing a charge current flowing into the page, indicated by the x in the circle, and a resulting spin current flowing to the reference layer / SAF for orienting the reference layer. [Figure 8]

[0016] FIG. 8A and FIG. 8B are schematic diagrams of a TMR sensor having series-connected pillars coupled to respective terminals for measuring voltages VTMR1 and VTMR2, respectively. [Figure 8C]

[0017] This is a schematic diagram of the sensor of FIG. 8B having a floating voltage source coupled across the pillars and a floating voltage source coupled across the HM layer. [Figure 9]

[0018] FIG. 9A is a schematic diagram of an exemplary TMR sensor having two serially connected devices with independent control of the ferromagnetic layer by respective SOT currents, and FIG. 9B is a schematic diagram of an exemplary TMR sensor having two serially connected devices with independent control of the ferromagnetic layer by respective SOT currents along with independent reading of two TMR pillars. [Figure 10A]

[0019] FIG. 2 is a schematic diagram of an exemplary TMR sensor having serially connected devices when the charge current to the HM layer and the TMR read operation do not occur simultaneously. [Figure 10B]

[0020] FIG. 2 is a schematic diagram of an exemplary sensor including serially connected devices when the charge current to the HM layer and the TMR read operation occur simultaneously. [Figure 11A]

[0021] FIG. 2 is a schematic diagram of an exemplary TMR sensor having electrical isolation between the HM layer and the TMR device. [Figure 11B]

[0022] FIG. 11A is a schematic diagram of an exemplary sensor that shares some commonalities with the sensor of FIG. 11A, but includes an insulating layer between a ferromagnetic material extending upward to the barrier material and a ferromagnetic material extending downward to the HM layer. [Figure 11C]

[0023] FIG. 2 is a schematic diagram of an exemplary sensor having electrical isolation between the HM layer and the TMR device. [Figure 12]

[0024] FIG. 12A is a schematic diagram of an exemplary GMR sensor having an antiferromagnetic (AF) layer and a copper spacer disposed within the ferromagnetic material, and FIG. 12B is a schematic diagram of an exemplary GMR sensor in which the HM layer replaces the AF layer. [Figure 13]

[0026] FIG. 13A is a schematic diagram of an exemplary GMR sensor having an insulating layer on the HM layer, and FIG. 13B is a schematic diagram of an example GMR configuration including an insulating layer between a ferromagnetic material extending upward to the spacer and a ferromagnetic material extending downward to the HM layer. [Figure 14A]

[0028] This is a schematic diagram of an exemplary sensor having SOT control of the free layer. [Figure 14B]

[0029] This is a graph of the response related to the sensor in Figure 14A. [Figure 14C]

[0030] This is a schematic diagram of an exemplary sensor having a stack-up similar to the sensor in Figure 14A, but with different operating characteristics. [Figure 14D]

[0031] This is a schematic diagram of an exemplary AF-based MR sensor having a feedback coil coupled to an amplifier AMP for canceling out the detected external magnetic field. [Figure 14E]

[0032] This figure shows further details regarding the sensor in Figure 14C. [Figure 14F]

[0033] This is a schematic diagram of an exemplary sensor having an AF layer, a reference layer, a barrier layer, a free layer, an insulating layer, and an HM layer containing a first SOT current Icharge1 having a first direction and a second SOT current Icharge2 having a second direction. [Figure 14G]

[0034] This figure shows further details of the sensor in Figure 14F, which has SOT control of the free layer by first and second charge currents Icharge1 and Icharge2 having different directions within the HM layer. [Figure 15]

[0035] This is a schematic diagram of an exemplary sensor having SOT control of the free layer in a TMR device having pillars connected in series. [Figure 16A]

[0036] This is a side view of an exemplary sensor having SOT control of the free layer in a device having multiple pillars connected in series. [Figure 16B] This is an isometric view of an exemplary sensor having SOT control of the free layer in a device having multiple pillars connected in series. [Figure 17]

[0037] This is a schematic diagram of an exemplary sensor having an SOT current Icharge in the HM layer to control the reference layer without separation of the ferromagnetic material. [Figure 18]

[0038] This is a schematic diagram of an exemplary sensor having an insulating layer between the HM layer and the reference layer. [Figure 19]

[0039] This is a schematic diagram of an exemplary TMR sensor having an SOT-controlled reference layer. [Modes for carrying out the invention]

[0010]

[0040] Figure 1 shows an exemplary magnetic field sensor 10 having at least one magnetic field sensing element 12, which includes one or more MR elements having SOT tuning according to an exemplary embodiment of the present disclosure, as will be shown and described in more detail below. The sensor 10 is configured to generate a magnetic field signal 16 indicating a magnetic field associated with a target 18, and the detector 20 is configured to generate a sensor output signal 28, which includes transitions associated with a feature of the target, in response to the magnetic field signal and a threshold level from a threshold generator 24, and in response to the magnetic field signal crossing the threshold level.

[0011]

[0041] The target 18 is not limited to a gear having gear teeth 18a-18c or a ring magnet having one or more pole pairs, but can take various forms including these. Furthermore, a linear configuration of a linearly moving ferromagnetic object is also possible. In the exemplary embodiment shown in Figure 1, the magnetic field sensor 10 may take the form of a rotational detector for detecting the teeth of a passing gear, for example, of a ferromagnetic gear, or more generally, the gear teeth 18a-18c of the target object 18. The permanent magnet 22 can be positioned at various locations close to the gear 18, and when the gear rotates in a so-called "reverse bias" configuration, fluctuations in the magnetic field close to the gear result.

[0012]

[0042] A characteristic of target 18 is that it is spaced apart from the sensing element 12 by an air gap. Even though the sensor 10 is intended to be fixed in place after being positioned for a specific application, the air gap can vary for various reasons. The difference between the angle of transition of the sensor output signal 28 and the location of the relevant features 18a-18c of target 28 is called the "hard offset".

[0013]

[0043] The sensing element 12 can take various forms, such as a TMR element, which can be arranged in one or more bridge configurations or other configurations to generate one or more single-ended or differential signals indicating the detected magnetic field. The front-end amplifier 30 can be used to process the output signal of the magnetic field sensing element to generate a further signal for coupling to an analog-to-digital converter (ADC) 34, which may include one or more filters, such as a low-pass filter and / or a notch filter, and may take the form of a sigma-delta modulator to generate the digital magnetic field signal 16. Features of the magnetic field signal processing may include a front-end reference 32 and a sigma-delta reference 36.

[0014]

[0044] The sensor 10 includes a power management unit (PMU) 40 which may contain various circuits for performing power management functions. For example, a regulator 42 can output a regulated voltage (VREGA: voltage for powering analog circuitry of the sensor) to power the sensor's analog circuitry and / or a regulated voltage (VREGD: voltage for powering digital circuitry of the sensor) to power the sensor's digital circuitry. A bias current source 46, a temperature monitor 50, and an undervoltage lockout 54 can monitor current, temperature, and voltage levels and provide relevant status signals to the digital controller 60. A clock generation element 56 and an oscillator 58 are coupled to the digital controller 60.

[0015]

[0045] The digital controller 60 processes the magnetic field signal 16 to determine the speed, position, and / or direction of movement of the target 18, such as rotation, and outputs one or more digital signals to the output protocol module 64. More specifically, the controller 60 can determine the speed, position, and / or direction of the target 18 based on the magnetic field signal 16 and combine this information with fault information in some embodiments to generate various forms of sensor output signals 28. The output of the module 64 is supplied to an output driver 66 that provides various forms of sensor output signals 28, such as so-called two-wire or three-wire formats, in which case the output signal is provided in the form of current pulses over a power connection to the sensor, and in which case the output signal is provided over a separate dedicated output connection. The output signal 28 can take various forms, such as pulse-width modulated (PWM) signal format, single-edge nibble transmission (SENT) format, serial peripheral interface (SPI) format, local interconnect network (LIN) format, controller area network (CAN) format, and inter-integrated circuit (I) format. 2 The signal can be in the form of an Inter-Integrated Circuit (C) or other similar signal formats. The sensor 10 may also include electrostatic discharge (ESD) protection 70.

[0016]

[0046] The digital controller 60 includes a detector 20, a threshold generator 24, and a memory 26 such as EEPROM 26a, 26b. The memory 26 can be used to store values ​​related to various sensor functions, including storing function coefficients used by the threshold generator 24 when generating an adaptable threshold level for use by the detector 20.

[0017]

[0047] The detector 20 is coupled to receive the threshold level and magnetic field signal 16 thus generated, and compares the received levels to generate a binary, two-state detector output signal with a transition when the signal 16 crosses the threshold level. The moving speed of the target 18 can be detected depending on the frequency of the binary signal.

[0018]

[0048] It should be understood that the rotation direction of the target 28 may be determined in embodiments including a plurality of sensing elements 12 configured to generate phase-separated magnetic field signals (sometimes called channel signals), in which case the rotation direction may be determined based on the relative phase difference or relative time difference (e.g., lag or lead) of specific edge transitions of the detector output signals associated with the phase-separated magnetic field signals.

[0019]

[0049] It is understood that embodiments of MR-based sensing elements are useful in a wide range of magnetic sensors. While exemplary sensors are shown and described above, it is possible to provide any practical magnetic sensor in which it is desirable to have an MR sensing element present. For example, MR sensing elements are useful in many magnetic position and angle sensors requiring high resolution. Further exemplary sensors in which an MR-based sensing element is present are shown and described below.

[0020]

[0050] Figure 2 shows an exemplary TMR bridge 200 having a first resistor R1, a second resistor R2, a third resistor R3, and a fourth resistor R4 coupled in a bridge configuration, which can correspond to the sensing element 12 of Figure 1. The first terminal T1 is coupled to a voltage source, and the second terminal T2 is coupled to ground (or other potential). The third terminal T3 provides a first differential output signal Vo-, and the fourth terminal T4 provides a second differential output signal Vo+. The differential outputs Vo+, Vo- of the bridge can be supplied to an amplifier AMP, or to other circuits for processing the output of the magnetic field sensing element as described above.

[0021]

[0051] Figure 3 shows an exemplary implementation in which a bridge resistor R1 includes 16 pillars P1-16 that provide the total resistance to R1. It is understood that a TMR resistor that realizes the bridge section can have any practical number of pillars connected in series and / or parallel to realize a TMR bridge resistor. The pillars can be designed to have the same or different resistances.

[0022]

[0052] Figure 4 shows an exemplary magnetic tunnel junction (MTJ) that uses TMR to realize a TMR element, such as a pillar. As is known in the art, tunneling magnetoresistance (TMR) occurs in a magnetic tunnel junction (MTJ), which has a first ferromagnetic material FM1 and a second ferromagnetic material FM2 separated by a thin insulating layer IL, such as MgO. The upper contact UC may be located on the first ferromagnetic material FM1, and the lower contact LC may be located on the second ferromagnetic material FM2. A substrate S can support the MTJ structure. The insulating layer must be thin, on the order of one nanometer, in order to allow electrons to "pass through" from one ferromagnetic material to another. It will be understood that this is a quantum mechanical phenomenon.

[0023]

[0053] The two magnetization directions of the ferromagnetic films FM1 and FM2 can be individually switched by an external magnetic field. When the magnetizations are in parallel orientations, electrons are more likely to pass through the insulating film IL than when the magnetizations are in opposite (antiparallel) orientations. As a result, such a junction can be switched between two states of electronic resistance, one with low resistance and the other with high resistance.

[0024]

[0054] The directions of FM1 and FM2 do not necessarily need to be switched: when the external magnetic field angles are neither parallel nor antiparallel, the resulting magnetization is understood to vary depending on the combined angle between the external magnetic field and the reference layer. The variation in resistance is proportional to the cosine of such combined angle, which makes the TMR element useful for angle sensing applications.

[0025]

[0055] Electrons with a specific spin orientation ("spin-up" or "spin-down") can pass from one ferromagnetic layer through a thin, non-conductive insulating layer to another ferromagnetic layer, provided that there are available free states with the same spin orientation. In the parallel state case, majority spin ("spin-up") and minority spin ("spin-down") electrons can pass through to the second ferromagnetic layer, filling it with a majority ("up") state and a minority ("down") state, respectively. This results in high conductance and corresponds to a low resistance state. In the antiparallel state case, majority spin ("spin-down") and minority spin ("spin-up") electrons from the first ferromagnetic layer fill the second ferromagnetic layer with a minority ("down") state and a majority ("up") state, respectively. This results in low conductance and corresponds to a high resistance state. Tunnel magnetoresistance is described in J. Mathon, Theory of Tunneling Magnetoresistance, 76 PHASE TRANSITIONS 491-500 (2003), which is incorporated herein by reference.

[0026]

[0056] Figure 5 shows an example of a ferromagnetic layer / heavy metal layer with a spin-orbit torque (SOT) configuration. During SOT operation, electrical charge currents flowing through spin-orbit (SO) materials such as heavy metals are converted into transverse pure spin currents that can act on adjacent layers such as Co, CoFe, CoFeB, or NiFe through the transfer of spin angular momentum, etc. This transfer of spin results in a magnetic torque acting on the ferromagnet, thereby changing its magnetization M. Typically, the current is 10 11 A·m -2 It is in the order of magnitude. As used herein, the heavy metal layer refers to a metal with a high atomic weight that exhibits strong orbital bonding. Exemplary materials include Pt, Ta, W Pd, and Ir.

[0027]

[0057] The resulting torque exerted on the ferromagnetic layer includes a first component called the DL (damping-like) magnetic field and a second component called the FL (field-like) magnetic field. The FL magnetic field is flat in the plane of the ferromagnetic layer, and the DL magnetic field is perpendicular to the plane. Exemplary embodiments of an MR sensor with SOT adjustment, as described more fully below, use the FL or DL ​​magnetic field to control the reference layer and / or free layer.

[0028]

[0058] Figure 6A shows a spin valve having a ferromagnetic layer separated by a spacer layer. Figure 6B shows a spin valve having a ferromagnetic layer separated by a spacer layer and an antiferromagnetic layer for orienting a reference layer. Figure 6C shows a spin valve having a ferromagnetic layer separated by a spacer layer, an antiferromagnetic layer for orienting a reference layer and a synthetic antiferromagnetic (SAF) layer for orienting a reference layer.

[0029]

[0059] FIG. 7A shows a charge current flowing into the page, indicated by an x in a circle, and a resulting spin current that flows to a reference layer including an in-plane FL magnetic field for orienting the reference layer. FIG. 7B shows a charge current flowing into the page, indicated by an x in a circle, and a resulting spin current that flows to a reference layer / SAF to orient the reference layer.

[0030]

[0060] FIG. 8A shows voltage V TMR1 , V TMR2 shows a TMR sensor 800 having a first pillar 802 and a second pillar 804 connected in series, coupled to respective terminals for measuring . The reference layer 806 is oriented by the AF layer 808 and separated from the free layer 810 by the barrier layer 812. The TMR current I TMR flows when V TMR1 -V TMR2 >0.

[0031]

[0061] FIG. 8B shows voltage V TMR1 , V TMR2 shows a TMR sensor 850 having a first pillar 852 and a second pillar 854 connected in series, coupled to respective terminals for measuring . The reference layer 856 is oriented by the FL magnetic field from the charge current Icharge in the heavy metal (HM) layer 860 when spin current flows upward toward the reference layer. The charge current direction may define the axis of sensitivity for the sensor. In the illustrated embodiment, the FL magnetic field orientation is an orientation into the page, as indicated by an x in a circle. In embodiments, the charge current Icharge, which may sometimes be referred to as SOT current, flows across the HM layer 860 when V 1SOT -V 2SOT >0. In the illustrated embodiment, the current I TMR flows through the first pillar 852 into the HM layer 860, while bypassing the second pillar 854 if the applied SOT current is applied concurrently with a pillar read operation, with a common ground reference, for example, V TMR2 and V 2SOT are coupled to ground.

[0032]

[0062] Figure 8C shows the sensor of Figure 8B, which includes a sensor 850' having a floating voltage source coupled across the pillar and a floating voltage source coupled across the HM layer. In the illustrated embodiment, the first voltage source V FLOATING1 It is coupled across the terminals for the first TMR pillar 852 and the terminals for the second TMR pillar 854, and the second voltage source V FLOATING2 This is coupled across the HM layer 860. This configuration allows the TMR current I TMR While reading the signal, a charge current Icharge can be injected into the HM layer 860. This configuration is operable for two pillars connected in series.

[0033]

[0063] Figure 9A shows a TMR sensor 900 having two series-connected devices, each having independent control of the ferromagnetic layer by its respective SOT current. The first pillar 902 is coupled to the first HM layer 904 with first voltage sources VFS11, VFS12 coupled across the first HM layer to generate a first SOT current Ipt1. The second pillar 906 is coupled to the second HM layer 908 with second voltage sources VFS11, VFS22 coupled across the second HM layer 908 to generate a second SOT current Ipt2. In the illustrated embodiment, the SOT currents Ipt1 and Ipt2 flow in opposite directions. The TMR current Itmr flows from the first pillar 902 to the second pillar 906, and this is the current flowing between the first floating voltage source and the second floating voltage source. Figure 9B shows an additional third floating voltage source V1TMR, VTMR2 coupled across the terminals for the first pillar 902 and the terminals for the second pillar 906 to enable TMR voltage reading operation. In some configurations, the floating voltage source is limited to two pillars connected in series.

[0034]

[0064] Figure 10A shows a TMR sensor 1000 with devices connected in series when there is no simultaneous charge current to the HM layer and no TMR reading operation. The first TMR device 1002 includes a first pillar 1004 and a second pillar 1006 on the first HM layer 1008, through which a charge current Icharge can flow. The second TMR device 1010 similarly includes a third pillar 1012 and a fourth pillar 1014 on the second HM layer 1016. The second pillar 1006 and the third pillar 1012 are electrically connected. Terminal V for the first pillar 1004 TMR1 and terminal V for the fourth pillar 1014 TMR2 The voltage across the range can be read. A switch 1020, such as a transistor, can be coupled between each TMR device 1002 and 1010.

[0035]

[0065] When switch 1020 is ON, the SOT current Icharge is applied to orient the reference (ref) magnetization (V1SOT - V2SOT > 0). The TMR terminals VTMR1 and VTMR2 are floating. When the SOT current Icharge is switched OFF by turning off switch 1020, the reference layer maintains its orientation due to the anisotropy of the ferromagnetic material.

[0036]

[0066] When the TMR voltage is read, switch 1020 is off: VTMR1 - VTMR2 > 0.

[0037]

[0067] It should be noted that it is impossible for the reference layer to be oriented by spin current simultaneously with the TMR reading operation. The spin current is used solely to switch the reference layer to a stable orientation.

[0038]

[0068] Figure 10B shows a series-connected device when charge current and TMR reading operation are simultaneously performed on the HM layer. First floating voltage source V FLOATING1It is coupled across the first pillar 1004 and the fourth pillar 1014 of the TMR device to the second floating voltage source V FLOATING2 This is coupled across the first HM layer 1008 for the first device to generate the first SOT current, and the third floating voltage source V FLOATING3 These are bonded across the second HM layer 1016.

[0039]

[0069] In this configuration, a floating voltage source is used without a common ground reference to enable simultaneous charge current and TMR reading operations within the HM layer.

[0040]

[0070] Figure 11A shows an exemplary TMR sensor 1100 having electrical isolation between the HM layer 1102 and the TMR device 1104. An insulating layer 1106 is positioned between the ferromagnetic layer 1107, which provides the first pillar 1108 and the second pillar 1110, and the HM layer 1102. The SOT current I charge passing through the HM layer 1102 generates an FL magnetic field as the spin current flows upward to the ferromagnetic layer 1107. This can be called an HM / insulating / ferromagnetic configuration.

[0041]

[0071] Thanks to the insulating layer 1106, the TMR current I TMR The current flows through the series-connected pillars 1108 and 1110, and the low ferromagnetic layer 1107, which is in contact with the insulating layer, is held in place while remaining magnetically controlled by the charge current Icharge flowing through the heavy metal layer 1102.

[0042]

[0072] The insulating layer 1106 must provide electrical insulation between the ferromagnetic layer 1107 and the HM layer 1102. Therefore, the TMR current 1114 flows through the tunnel barrier 1116 of the series-connected pillars 1108 and 1110 instead of flowing to the HM layer 1102. Furthermore, the insulating layer 1106 should enable the transmission of the FL magnetic field 1118 thanks to its good conductivity of spin currents or Rashba coupling.

[0043]

[0073] In some embodiments, the insulating layer 1106 material provides the above-mentioned properties (FL magnetic field transmission with electrical isolation and direct coupling (e.g., ferromagnetic insulator)). In other embodiments, the properties are synthesized by a non-magnetic but insulating layer and magnetic coupling (e.g., rough Neel coupling, RKKY coupling, direct coupling through pinholes). The layer(s) may have a nanometer thickness.

[0044]

[0074] It is understood that any suitable material can be used for the insulating layer to meet the specific application needs. Exemplary materials include ferromagnetic or ferrimagnetic insulators, e.g., CoFe2O4, MgTiO3, spinel ferrite, YIG, TIG, manganese salts, antiferromagnetic insulators, e.g., NiO or CoO, and / or nonmagnetic insulators, e.g., MgO.

[0045]

[0075] Figure 11B shares some commonalities with the sensor in Figure 11A, however, it shows an embodiment 1150 which includes an insulating layer 1152 between a ferromagnetic material 1154 extending upward to the barrier material 1156 and a ferromagnetic material 1158 extending downward to the HM layer 1160. This can be considered an HM / ferromagnetic / insulating / ferromagnetic configuration. In this configuration, the ferromagnetic material 1158 is in direct contact with the HM layer 1160 and is magnetically coupled to the ferromagnetic material 1154 below the barrier 1156 through the insulating layer 1152.

[0046]

[0076] Figure 11C shows an exemplary sensor 1170 having electrical isolation between the HM layer and the TMR device. The first TMR device 1172 and the second TMR device 1174 are electrically coupled by terminals coupled across the first pillar 1176 and the fourth pillar 1178. A voltage source V across the HM layer 1180 1SOT , V 2SOT This generates SOT current I charge within the HM layer. TMR current I TMR The material flows through the pillars of devices 1172 and 1174, including a conductive material 1175 that connects the first TMR device 1172 and the second TMR device 1174.

[0047]

[0077] This configuration allows any practical number of pillars to be connected in series to suit the needs of a particular application.

[0048]

[0078] In another embodiment, as shown in Figure 11B, the insulating layer can be positioned between the ferromagnetic material extending to the barrier layer and the ferromagnetic material extending to the HM layer.

[0049]

[0079] Figure 12A shows an exemplary GMR sensor 1200 having an antiferromagnetic (AF) layer 1202 and a copper spacer 1204 disposed within a ferromagnetic material. The AF GMR current is I GMR The current flows parallel to the plane of the AF layer 1202 along the copper spacer.

[0050]

[0080] Figure 12B shows an exemplary GMR sensor in which the HM layer 1250 replaces the AF layer. The SOT current is supplied by the voltage source V 1SOT , V 1SOT This is generated by this configuration, which results in a GMR current I GMR A portion of it bypasses into the HM layer 1250, thereby canceling out part of the GMR effect.

[0051]

[0081] Figure 13A shows an exemplary GMR sensor 1300 having an insulating layer 1302 on an HM layer 1304. A reference layer 1306 and a free layer 1308 are separated by a spacer 1310 made of copper or the like. The GMR voltage is measured at terminal V GMR1 , V GMR2 It can be read in the following location. The SOT current Icharge is the voltage source V across the HM layer 1304. 1SOT , V 2SOT This generates a spin current within the HM layer, and therefore, a spin current flows upward from the HM layer. While maintaining control of the reference layer 1306 by the operating FL magnetic field, the insulating layer 1302 separates the GMR structure from the HM layer 1304.

[0052]

[0082] Figure 13B shows a similar configuration in which an insulating layer 1350 is provided between a ferromagnetic material 1352 extending upward to the spacer 1310 and a ferromagnetic material 1354 extending downward to the HM layer 1304.

[0053]

[0083] Figure 14A shows an exemplary sensor 1400 having SOT control of the free layer 1402. The antiferromagnetic (AF) layer 1404 is adjacent to the reference layer 1406, which is separated from the free layer 1402 by a barrier layer 1408. The insulating layer 1410 is located between the free layer 1402 and the HM layer 1412. The SOT current Icharge can flow through the HM layer 1412.

[0054]

[0084] The external magnetic field to be detected is parallel to the charge current Icharge in the HM layer 1412 and perpendicular to the FL magnetic field applied to the free layer 1402 by the spin current induced by the charge current. The FL magnetic field bias modulates the sensitivity of the stack so that the stack sensitivity is modulated by the charge current. The reference layer 1406 is blocked by the AF layer in the AF / ferromagnetic configuration.

[0055]

[0085] Figure 14B shows a graph of the response for sensor 1400 in Figure 14A. The charge current and FL magnetic field are perpendicular to the sensor's sensitivity axis and linearize the sensor response to the external magnetic field 1430. As can be seen, the larger the Icharge 1432 and FL magnetic field 1434, the lower the sensor sensitivity becomes. Sensitivity can be dynamically modulated by varying Icharge. The magnetic field gradient can be a factor in sensor sensitivity.

[0056]

[0086] In embodiments, sensitivity control is desirable in various applications. For example, a sensor positioned relatively far from the target may require a higher sensitivity level than a sensor positioned relatively close to the target. It is understood that adjusting the dynamic range of the sensor is desirable in various sensor applications.

[0057]

[0087] Figure 14C shows an exemplary sensor 1450 having a stack-up similar to sensor 1400 in Figure 14A, but with different operating characteristics. The external magnetic field to be detected is perpendicular to the charge current Icharge and parallel to the FL magnetic field applied to the free layer 1402 by the spin current induced by the charge current. The FL magnetic field bias can be used to cancel out the external magnetic field in a feedback loop configuration. As will be easily understood, this configuration eliminates the need for a feedback loop coil used in conventional sensors.

[0058]

[0088] In embodiments, the SOT current is controlled to generate an FL magnetic field to cancel out an external magnetic field in a manner desirable in a closed-loop sensor configuration. For example, it may be desirable to cancel out only a portion of the external magnetic field, or to cancel it in a manner that suits the needs of a particular application. In embodiments, the cancellation of the SOT magnetic field can be, for example, 5 to 10 times larger than coil-based cancellation for the same current level.

[0059]

[0089] Figure 14D shows an AF-based MR sensor having a feedback coil coupled to an amplifier AMP for canceling the detected external magnetic field. Figure 14E shows further details of sensor 1450 in Figure 14C, which includes a sense resistor SR coupled to the amplifier AMP, which can replace the feedback coil in Figure 14D. The feedback current is injected directly into the HM layer 1412 to generate a charge current Icharge, which gives rise to a spin current and an FL magnetic field that cancels out the external magnetic field to be detected.

[0060]

[0090] Figure 14F shows an exemplary sensor 1470 having an AF layer 1404, a reference layer 1406, a barrier layer 1408, a free layer 1408, an insulating layer 1410, and an HM layer 1472. In the illustrated embodiment, a first SOT current Icharge1 has a first direction, and a second SOT current Icharge2 has a second direction. The first SOT current Icharge1 can generate a first FL magnetic field in the direction of the applied external magnetic field and can be used to cancel out the magnetic field in the feedback loop configuration. The second SOT current Icharge2 generates a second FL magnetic field perpendicular to the external magnetic field. The second FL magnetic field acts as a bias to modulate the sensitivity of the sensor.

[0061]

[0091] Figure 14G shows further details of the sensor of Figure 14F, which, as described above, has SOT control of the free layer by first and second charge currents Icharge1 and Icharge2 having different directions within the HM layer. The first SOT current Icharge1 is controlled so that a feedback current is injected directly into the HM layer to generate a magnetic field that cancels out the applied external magnetic field. The second SOT current Icharge1 can be used to linearize the stacking response.

[0062]

[0092] Figure 15 shows an exemplary sensor 1500 with free layer SOT control in a TMR device having pillars connected in series. In the illustrated embodiment, a first free layer 1502a is shared by first and second pillars 1504, 1506, each having barriers 1508a, 1508b, reference layers 1510a, 1510b, and AF layers 1512a, 1512b. Third and fourth pillars 1514, 1516 have a similar stack-up on the shared second free layer 1502b. The first free layer 1502a and the second free layer 1502b are connected to an insulating layer 1518 on an HM layer 1520, and an SOT current Icharge may flow through the HM layer 1520 to control the free layer 1502.

[0063]

[0093] Figure 16A is a side view and Figure 16B is an isometric view of a sensor 1600 having SOT control of the free layer in a device having multiple pillars connected in series. The first pillar 1602a includes a lamination of an AF layer 1604, a reference layer 1606, a barrier 1608, and a free layer 1610. The second pillar 1602b includes a similar lamination. The first and second pillars 1602a, 1602b are arranged on an insulating layer 1612 on an HM layer 1614. A metallic material 1616 is connected between the free layer 1610a of the first pillar 1602a and the free layer 1610b of the second pillar 1602b. In the illustrated embodiment, the metallic material 1616 is on the insulating layer 1612 so as to completely fill the region between the free layers 1610a and 1610b.

[0064]

[0094] Figure 17 shows an exemplary sensor 1700 having a SOT current Icharge within the HM layer 1702 to control the reference layer 1704 without involving the separation of ferromagnetic material. The charge current Icharge is applied to switch the reference layer 1704 in a stable direction, but it is not possible to apply it when reading the TMR.

[0065]

[0095] Figure 18 shows an exemplary sensor 1800 having an insulating layer 1802 between the HM layer 1804 and the reference layer 1806. The charge current Icharge in the HM layer 1804 can be controlled, thanks to the isolation layer, so that the FL magnetic field can be applied simultaneously with the TMR reading operation. In the embodiment, the orientation of the FL magnetic field can be varied from 0 to 360 degrees from the reference point by adjusting the direction and magnitude of the first and second charge currents Icharge1 and Icharge2 in the HM layer 1804.

[0066]

[0096] In embodiments, the sensor may have a "zero" position defined by first and second charge currents Icharge1 and Icharge2. The deviation from the zero position can be determined in a manner that suits the needs of a particular application.

[0067]

[0097] Figure 19 shows an exemplary TMR sensor 1900 having an SOT-controlled reference layer. In the illustrated embodiment, the first, second, and third pillars 1904a, 1904b, and 1904c are connected to an insulating layer 1906. The first and second pillars 1904a and 1904b have a common reference layer 1902. Each pillar 1904 is controlled by its respective HM layer 1908 having its respective first and second charge currents Icharge1 and Icharge2. TMR current I TMR It flows downward through the first pillar 1904a as shown, through a common reference layer to the second pillar 1904b, up through the second pillar, and through the conductor 1910 to reach the third pillar 1904c.

[0068]

[0098] In some embodiments, the SOT control of the reference layer allows switching of the reference orientation at relatively high frequencies, such as nanoseconds to microseconds, to enable cancellation of 1 / f electron noise and offset using known chopping techniques. In other embodiments, the reference layer can be oriented at any angle from 0 to 360 degrees. This enables an angle sensor based on the variation in TMR resistance according to the angle between the reference layer set by the SOT current and the free layer set by the external magnetic field. The orientation of the external magnetic field may match the reference orientation that produces the minimum TMR resistance when the reference is rotated from 0 to 360 degrees by the SOT current.

[0069]

[0099] It is understood that exemplary sensor embodiments may include any practical number of pillars. Generally, increasing the number of pillars increases the signal-to-noise ratio (SNR) of the sensor. In some embodiments, hundreds or thousands of pillars may be used.

[0070]

[0100] Exemplary embodiments of MR sensors with SOT layer control offer advantages over known MR sensors. For example, controlling ferromagnetic magnetization by applying current through a heavy metal (HM) provides far greater versatility in manufacturing the sensor compared to the normal interaction between the antiferromagnetic and ferromagnetic layers. In some embodiments, the magnetic orientation of the ferromagnetic layer can be set to any direction by applying a current in a selected direction to the heavy metal layer in contact with the ferromagnetic layer, using a dedicated HM layer configuration. The intensity of the FL magnetic field applied to the ferromagnetic layer can also be modulated by changing the amplitude of the current in the HM layer. The ferromagnetic layer can further be switched at higher frequencies than in conventional sensors. Exemplary sensor embodiments include dynamic sensing characteristics such as reduced noise due to high-frequency switching of the reference and reduced current in the feedback loop architecture.

[0071]

[0101] As used herein, the terms “anisotropy” or “anisotropic” refer to a specific axis or direction in which the magnetization of a ferromagnetic or ferrimagnetic layer tends to point when not subjected to further external magnetic fields. Axial anisotropy can be produced by crystallographic effects or geomorphic anisotropy, both of which allow for two equivalent directions of magnetic fields. Directional anisotropy can also be produced in adjacent layers, for example by an antiferromagnetic layer, thereby allowing only a single magnetic field direction along a specific axis within adjacent layers.

[0072]

[0102] In light of the above, the introduction of anisotropy in the magnetic layer can be understood as compelling the magnetization of the magnetic layer to align along the anisotropy when there is no external magnetic field. In the case of GMR or TMR elements, directional anisotropy provides the ability to obtain, for example, a coherent rotation of the magnetic field in the magnetic layer in response to an external magnetic field.

[0073]

[0103] In general, magnetic materials can have a variety of magnetic properties and can be classified by a range of terms and names, including but not limited to ferromagnetic, antiferromagnetic, and nonmagnetic materials. A detailed description of the various types of magnetic materials is not provided herein. However, here we will simply state that ferromagnetic materials are those in which the magnetic moments of atoms tend to align, on average, in parallel and in the same direction, resulting in a non-zero net magnetic magnetization.

[0074]

[0104] Antiferromagnetic materials are materials in which the magnetic moments within the antiferromagnetic material tend to be aligned in parallel but opposite directions on average within the sublayers of the antiferromagnetic material, resulting in zero net magnetization.

[0075]

[0105] As is known, some of the above-mentioned magnetic field sensing elements tend to have an axis of maximum sensitivity parallel to the substrate supporting the magnetic field sensing element, while other parts of the above-mentioned magnetic field sensing elements tend to have an axis of maximum sensitivity perpendicular to the substrate supporting the magnetic field sensing element. In particular, planar Hall elements tend to have an axis of sensitivity perpendicular to the substrate, while metal-based or metallic magnetoresistive elements (e.g., GMR, TMR, AMR) and vertical Hall elements tend to have an axis of sensitivity parallel to the substrate.

[0076]

[0106] As used herein, the term “magnetic field sensor” is used to describe a circuit that uses a magnetic field sensing element in combination with other circuits. Magnetic field sensors are used in a variety of applications, including, but are not limited to, angle sensors that detect the angle of direction of a magnetic field, current sensors that detect a magnetic field generated by an electric current carried by an electric conductor, magnetic switches that detect the proximity of ferromagnetic objects, rotational detectors that detect magnetic domains of passing ferromagnetic articles, such as a ring magnet or ferromagnetic target (e.g., the teeth of a gear) (where the magnetic field sensor is used in combination with a reverse-biased magnet or other magnets), and magnetic field sensors that detect the magnetic field density of a magnetic field. As used herein, the terms “target” and “magnetic target” are used to describe an object that will be detected or found by a magnetic field sensor or magnetic field sensing element.

[0077]

[0107] Various embodiments of the concepts, systems, devices, structures, and techniques to be protected are described herein with reference to the relevant drawings. Alternative embodiments can be devised without departing from the scope of the concepts, systems, devices, structures, and techniques described herein. Note that various connections and positional relationships (e.g., above, below, adjacent to, etc.) are indicated between elements in the following description and drawings. These connections and / or positional relationships may be direct or indirect unless otherwise indicated, and the described concepts, systems, devices, structures, and techniques are not intended to be limiting in this respect. Thus, a connection of entities may refer to either a direct or indirect connection, and a positional relationship between entities may be a direct or indirect positional relationship.

[0078]

[0108] As an example of an indirect positional relationship, in this specification, reference to forming layer "A" on layer "B" includes situations where one or more intermediate layers (e.g., layer "C") are located between layer "A" and layer "B," provided that the related properties and functionalities of layer "A" and layer "B" are not substantially altered by the intermediate layer(s). The following definitions and abbreviations will be used for the interpretation of the claims and specification. When used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having,” “contains,” or “containing,” or any other variation thereof, are intended to cover non-exclusive inclusion. For example, a composition, mixture, process, method, article, or apparatus comprising a list of elements is not necessarily limited to those elements alone and may include other elements not explicitly listed or specific to such composition, mixture, process, method, article, or apparatus.

[0079]

[0109] The use of ordinal terms such as “first,” “second,” and “third” in the claims to modify the claims does not in itself imply any priority, superiority, or order of any one claim over another or temporary order in which the acts of the method are performed, but is used merely as a label to distinguish the claims, to differentiate one claim having a particular name from another having the same name (apart from the use of ordinal terms).

[0080]

[0110] Unless otherwise specified, the term "substantially" refers to a value within ±10%. For example, a first direction that is "substantially" perpendicular to a second direction may refer to a first direction that is within ±10% in that it forms a 90° angle with the second direction.

[0081]

[0111] While exemplary embodiments of this disclosure have been described, it will be apparent to those skilled in the art that other embodiments incorporating those concepts may also be used. The embodiments included herein should not be limited to those disclosed, but rather should be limited only by the spirit and scope of the appended claims. All publications and references cited herein are expressly incorporated herein by reference in their entirety.

[0082]

[0112] Elements of different embodiments described herein may be combined to form other embodiments not specifically described above. Various elements described in relation to a single embodiment may also be provided separately or in any preferred subcombination. Other embodiments not specifically described herein are also within the scope of the following claims.

Claims

1. A magnetoresistive (MR) device having a ferromagnetic material, A heavy metal layer configured to conduct electric current, To generate a field-like (FL) magnetic field within the ferromagnetic material in response to the aforementioned charge current, an insulating layer between the ferromagnetic material and the heavy metal layer is configured to electrically insulate and magnetically couple the heavy metal layer and the ferromagnetic layer. A device equipped with the following features.

2. The device according to claim 1, wherein the MR device comprises a GMR device.

3. The device according to claim 1, wherein the MR device comprises a TMR device having a pillar.

4. The device according to claim 3, wherein the TMR device comprises a free layer, a barrier, and a reference layer.

5. The device according to claim 4, wherein the orientation of the free layer is controlled by the charge current.

6. The device according to claim 4, wherein the orientation of the reference layer is controlled by the charge current.

7. The device according to claim 1, wherein the insulating layer is configured to allow a spin current to pass through in order to generate the FL magnetic field.

8. The device according to claim 1, wherein the insulating layer is configured to generate the FL magnetic field via a Rashba coupling.

9. The device according to claim 1, wherein the insulating layer is configured to generate the DL magnetic field.

10. The device according to claim 1, wherein the insulating layer includes a ferrimagnetic insulator.

11. The device according to claim 1, wherein the insulating layer includes a ferromagnetic insulator.

12. The device according to claim 1, wherein the insulating layer comprises a first layer configured to achieve electrical isolation and a second layer for achieving magnetic coupling between the heavy metal layer and the ferromagnetic layer.

13. The device according to claim 1, wherein the insulating layer is located between a first portion and a second portion of the ferromagnetic layer, the first portion extending to a barrier, and the second portion extending to the heavy metal layer.

14. The device according to claim 13, wherein the first portion and the second portion of the ferromagnetic layer are magnetically coupled through the insulating layer.

15. The device according to claim 1, wherein the device comprises two or more TMR pillars.

16. The device according to claim 1, wherein the charge current is configured to control the sensitivity of the device to an applied external magnetic field in the free layer of the ferromagnetic material that is parallel to the direction of the charge current and perpendicular to the FL magnetic field.

17. The device according to claim 1, wherein the charge current is configured to at least partially cancel out an external magnetic field perpendicular to the direction of the charge current and parallel to the FL magnetic field in the free layer of the ferromagnetic material.

18. The device according to claim 1, wherein the charge current comprises a first charge current configured to generate the FL magnetic field in the direction of the applied external magnetic field, and a second charge current configured to control the sensitivity of the device to the applied external magnetic field.

19. The device according to claim 1, wherein the device is configured to detect an external magnetic field, generate a feedback current corresponding to the external magnetic field, and inject the feedback current into the heavy metal layer to form at least a portion of the charge current.

20. The MR device according to claim 1, comprising at least first, second, third, and fourth TMR pillars connected in series, wherein at least two of the first, second, third, and fourth TMR pillars share a common free layer.

21. The device according to claim 20, wherein the common layer is disposed on the insulating layer.

22. The MR device according to claim 1, comprising at least a first TMR pillar and a second TMR pillar, each of which has a free layer on the insulating layer, and further comprising a metallic material connecting the free layer of the first pillar and the free layer of the second pillar.

23. The device according to claim 1, wherein the charge current includes a first charge current and a second charge current configured to orient the reference layer of the TMR device to any orientation within a 360-degree rotation range in the plane of the reference layer.

24. The device according to claim 1, further comprising a TMR device having a resistance variation corresponding to the angle between the orientation of the reference layer and the orientation angle of the free layer set by an applied external magnetic field.

25. The device according to claim 1, wherein the charge current includes a first charge current and a second charge current configured to cancel out 1 / f electrical noise, where f is the switching frequency.

26. A step of employing a magnetoresistive (MR) device having a ferromagnetic material, The steps include employing a heavy metal layer configured to conduct electric current, The steps include setting an insulating layer between the ferromagnetic material and the heavy metal layer, configured to electrically insulate and magnetically couple the heavy metal layer, in order to generate a field-like (FL) magnetic field within the ferromagnetic material in response to the charge current, and Methods that include...

27. The method according to claim 26, wherein the MR device comprises a free layer, a barrier, and a reference layer.

28. The method according to claim 27, further comprising the step of controlling the orientation of the free layer with the charge current.

29. The method according to claim 27, further comprising the step of controlling the orientation of the reference layer with the charge current.

30. The method according to claim 26, wherein the insulating layer is configured to allow a spin current to pass through in order to generate the FL magnetic field.

31. The method according to claim 26, wherein the charge current includes a first charge current and a second charge current configured to orient the reference layer of the TMR device to any orientation within a 360-degree rotation range in the plane of the reference layer.

32. The method according to claim 26, wherein the MR device has a resistance variation corresponding to the angle between the orientation of the reference layer and the orientation angle of the free layer set by the applied external magnetic field.

33. A magnetoresistive (MR) device having a free layer, a barrier, and a reference layer, A heavy metal layer connected to the MR device and configured to carry first and second charge currents, wherein the first and second charge currents are configured to generate a field-like (FL) magnetic field to orient the reference layer within a range of 0 to 360 degrees, and A device equipped with the following features.

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