Magnetoresistive sensor element with compensated temperature sensitivity coefficient and method for manufacturing said element - Patents.com

Abstract

The temperature sensitivity, which is related to the magnetic susceptibility of the magnetoresistive sensor element, is improved. The present invention relates to a magnetoresistive sensor element (2), which comprises: a reference layer (23) having a pinned reference magnetization (23); a sense layer (21) having a free sense magnetization (210) with a stable vortex configuration that is reversibly movable in response to an external magnetic field (60) to be measured; a tunnel barrier layer (22) between the reference layer (23) and the sense layer (22); In a magnetoresistive sensor element (2) comprising: the sense layer (21) comprises a first ferromagnetic sense portion (211) in contact with the tunnel barrier layer (22) and a second ferromagnetic sense portion (212) in contact with the first ferromagnetic sense portion (211); The second ferromagnetic sense portion (212) contains a dilution element in a proportion such that the temperature dependence of the magnetic susceptibility (χ) substantially compensates for the temperature dependence of the tunneling magnetoresistance of the magnetoresistive sensor element. The present disclosure relates to a method for manufacturing a magnetoresistive sensor element.

Description

[Technical field]

[0001] The present invention relates to a magnetoresistive sensor element for use in a magnetic sensor intended for sensing an external magnetic field, and to a method for manufacturing a magnetoresistive sensor element. [Background technology]

[0002] Figure 1 shows a ferromagnetic reference layer 23 comprising a first ferromagnetic layer 231 having a first reference magnetization 234 and a second ferromagnetic layer 232 having a second reference magnetization 235; a sense ferromagnetic layer 21 having a free sense magnetization 210; A tunnel barrier layer 22 between the sense ferromagnetic layers 21 and 23; 2 shows a cross-sectional view of a magnetoresistive sensor element 2 comprising: a sense magnetization 210 that can be oriented in an external magnetic field 60 while the reference magnetizations 234, 235 remain substantially undisturbed. The external magnetic field 60 can thus be sensed by measuring the resistance of the magnetoresistive sensor element 2. The resistance depends on the relative orientations of the sense and reference magnetizations. It should be noted that the reference layer 23 may comprise a single reference layer with a pinned reference magnetization.

[0003] 2 a and 2 b show a top view of the sense layer 21 , where the sense magnetization 210 comprises a stable vortex configuration with a core 213 that is reversibly movable according to an external magnetic field 60 . The vortex configuration provides a linear and non-hysteretic behavior in a wide magnitude range of the external magnetic field 60 for a practical size of the magnetoresistive sensor element 2 and thickness of the sense layer 21. Thus, the vortex configuration is advantageous for 1D magnetic sensor applications. Obtaining the vortex configuration in the sense layer 21 depends on several factors, including the material properties of the sense layer 21. In general, the vortex configuration is favored by increasing the aspect ratio of the thickness to the diameter of the sense layer 21 (at zero applied magnetic field). The aspect ratio is typically much smaller than 1 (e.g., 0.01 to 0.5). More specifically, FIG. 2a shows the sense magnetization 210 in the absence of an external magnetic field 60, with the core 213 of the vortex configuration substantially in the center of the sense layer cross section. In this configuration, the sense layer 21 has a net magnetic moment that is substantially zero (M=0). 2b shows the sense magnetization 210 in the presence of an external magnetic field 60. The external magnetic field 60 causes the core 213 to move in a direction (indicated by the dotted arrow) that is substantially perpendicular to one of the external magnetic fields 60. The displacement of the core 213 results in a net magnetic moment (M≠0) in the sense layer 21. In particular, displacement of core 213 to the right (as shown in FIG. 2b) results in a net magnetic moment M>0 in sense layer 21, while displacement of core 213 to the left (not shown) results in a net magnetic moment M<0 in sense layer 21 when external magnetic field 60 is oriented opposite to the direction shown in FIG. 2b.

[0004] FIG. 3 shows the external magnetic field 60 (H ext , arbitrary units) of the hysteresis response (or magnetization curve) of the vortex sense magnetization 210. The complete hysteresis loop of the vortex sense magnetization 210 is shown in FIG. expl The applied magnetic field H ext At this point, the sense magnetization 210 is magnetically saturated. To restore the vortex state of the sense layer 21, a nucleation field H nucl It is necessary to reduce the magnetic field below + / - H. expl) the hysteretic response to the external magnetic field 60 has a reversible linear portion corresponding to the motion of the core 213 with the external magnetic field 60. The value and slope of the linear portion of the hysteresis loop is strongly dependent on the size of the sense layer 21. The linear, non-hysteretic portion of the magnetization curve is ext This makes it easier to measure small variations in

[0005] In particular, a vortex is characterized by its magnetic susceptibility, χ, which is the M(H) loop χ=δM / δH ext (1) corresponds to the slope of the linear region of

[0006] In this case, the sensitivity S of the magnetoresistive sensor element 2 is calculated by multiplying the magnetic susceptibility χ of the magnetoresistive sensor element 2 by the tunnel magnetoresistance (TMR) S=χ*TMR (2) will be proportional to the product between

[0007] 4a and 4b show an external magnetic field 60 (in arbitrary units of H ext ) shows the electrical conductance G (in arbitrary units) of the magnetoresistive sensor element 2 as a function of the magnetic field. FIG. 4 a reports the electrical conductance G when the sense magnetization 210 is parallel to the first reference magnetization 234 , and FIG. 4 b reports the electrical conductance G when the sense magnetization 210 is anti-parallel to the first reference magnetization 234 . The electrical conductance G of the magnetoresistive sensor element 2 can be measured by passing a read current 31 (see FIG. 1) through the magnetoresistive sensor element 2. The electrical conductance G of the magnetoresistive sensor element 2 is proportional to the projection of the averaged sense magnetization 210 onto the direction of the first reference magnetization 234, and so the electrical conductance G versus the external magnetic field H ext is the external magnetic field H ext is aligned with the direction of the first reference magnetization 234.

[0008] However, both the magnetic susceptibility χ and the TMR vary as a function of the temperature T. In particular, as the temperature T increases, the sense magnetization 210 decreases, which leads to an increase in the magnetic susceptibility χ. On the other hand, the TMR increases with temperature T. The temperature dependence of the magnetoresistive sensor element 2 is characterized by the temperature sensitivity coefficient (TCS), which corresponds to the change in sensitivity S with temperature T. Figure 5 reports the ratio of the sense magnetization M to the saturation sense magnetization Ms (arbitrary units). With the external magnetic field H ext (arbitrary units) at several temperatures of the magnetoresistive sensor element 2. The slope of the linear region, and therefore the magnetic susceptibility χ, is related to the increasing temperature. Figures 6a to 6c show the measured conductance curves, i.e., for three increasing temperatures T (Figures 6a to 6c), i.e., for an external magnetic field H ext We report the electrical conductance G (in arbitrary units) of the magnetoresistive sensor element 2 as a function of temperature (in arbitrary units). Figures 6a to 6c show that the TMR decreases with increasing temperature. TMR is the maximum change in resistance (or inverse conductance) of the magnetoresistive sensor element 2 relative to an external magnetic field H ext It is expressed as a function of .

[0009] In most cases, increasing temperature reduces the TMR faster than the magnetic susceptibility χ increases, leading to a large negative TCS. Thus, the TCS of a magnetoresistive sensor element 2 is a very important variable that can affect the sensing performance of the magnetoresistive sensor element 2 and the range of its potential practical applications.

[0010] The TCS can be controlled using electronic circuitry that compensates for changes in the sensitivity S of the magnetoresistive sensor element 2 over temperature by varying the bias voltage of the magnetoresistive element. This solution, however, requires trimming to adjust the TCS. Furthermore, the use of additional electronic circuitry requires a larger die size and makes the process and development of the magnetoresistive sensor element 2 more complex.

[0011] Patent Document 1 (US2018164387) a reference layer having a pinned reference magnetization; a sense layer having a free sense magnetization with a stable vortex configuration with a core that is reversibly movable in response to an external magnetic field to be measured; a tunnel barrier layer between the reference layer and the sense layer; A magnetic sensor comprising:

[0012] Patent Document 2 (US2017371006) discloses a GMR element comprising a pinned magnetic layer, a non-magnetic material layer, and a free magnetic layer exchange-coupled with a first antiferromagnetic layer. The free magnetic layer is composed of a first ferromagnetic layer and a magnetic adjustment layer. The magnetic adjustment layer contains at least one iron group element and at least one platinum group element. The magnetic adjustment layer reduces the saturation magnetization of the free magnetic layer, thereby increasing the magnitude of the exchange coupling bias Hex of the exchange coupling between the free magnetic layer and the first antiferromagnetic layer. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] US Patent Application Publication No. 2018 / 164387 [Patent Document 2] US Patent Application Publication No. 2017 / 371006 Summary of the Invention

[0014] The present disclosure relates to a magnetoresistive sensor element for sensing a one-dimensional (1D) external magnetic field. The magnetoresistive sensor element comprises: A sense layer having a free sense magnetization with a stable vortex configuration with a core that is reversibly movable in response to an external magnetic field. A tunnel barrier layer between the reference layer and the sense layer, the tunnel barrier layer comprising an insulating material. The sense layer includes a first ferromagnetic sense portion in contact with the tunnel barrier layer and a second ferromagnetic sense portion in contact with the first ferromagnetic sense portion. The second ferromagnetic sense portion contains a transition metal element in a proportion such that the temperature dependence of the magnetic susceptibility of the sense layer substantially compensates for the temperature dependence of the tunneling magnetoresistance of the magnetoresistive sensor element.

[0015] The present disclosure further relates to a method of manufacturing a magnetoresistive sensor element for a number of temperatures and ratios of transition metal elements, Measuring the electrical conductance G of the magnetoresistive sensor element as a function of an external magnetic field for a number of temperatures, e.g. obtaining a number of measured conductance curves; calculating a value of the TMR of the magnetoresistive sensor element from a plurality of measured conductance curves, e.g., for each temperature, to determine a temperature dependence of the TMR; and measuring the magnetization of the sense layer, e.g., to determine a temperature dependence of the magnetic susceptibility of the sense layer; determining a proportion of the transition metal element such that the temperature dependence of the TMR substantially compensates for the temperature dependence of the magnetic susceptibility; Effect of the Invention

[0016] The magnetoresistive sensor elements disclosed herein have minimal temperature dependence of sensitivity, or minimal TCS. They do not require additional on-board electronics to compensate for loss of sensitivity by adapting the bias voltage to each temperature. They allow for small die size and do not require extra testing time.

[0017] The invention will be better understood with the help of the description of embodiments given by way of example and illustrated in the figures. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 shows a cross-sectional view of a magnetoresistive sensor element with a sense layer. [Diagram 2] 2a and 2b show top views of a sense layer having a sense magnetization with a vortex configuration movable in an external magnetic field. [Diagram 3]FIG. 3 shows the complete hysteretic response of the sense magnetization to an external magnetic field. [Figure 4] FIG. 4a shows the electrical conductance of a magnetoresistive sensor element as a function of an external magnetic field when the sense magnetization is parallel to the reference magnetization, and FIG. 4b shows the electrical conductance when anti-parallel. [Diagram 5] FIG. 5 reports the ratio of the sense magnetization to the saturation sense magnetization as a function of the external magnetic field measured for several temperatures in a magnetoresistive sensor element. [Figure 6] 6a to 6c report the electrical conductance of a magnetoresistive sensor element as a function of the external magnetic field for increasing temperature. [Figure 7] FIG. 7 shows details of the sense layer 21, which includes a first ferromagnetic sensing portion and a second ferromagnetic sensing portion, according to one embodiment. [Figure 8] FIG. 8 shows the saturation magnetization as a function of temperature for various dilutions of the sense magnetization. [Figure 9] FIG. 9 reports the experimentally measured saturation magnetization as a function of temperature in the sense layer, the second ferromagnetic sense portion containing NiFe alloys with different contents of transition metal elements. [Figure 10] FIG. 10 reports the TCS values ​​for various dilutions achieved by adding Ta to the NiFe alloy of the second ferromagnetic sense part. [Figure 11] FIG. 11 shows details of the second ferromagnetic sense portion according to one embodiment. [Figure 12] FIG. 12 presents a Wheatstone bridge configuration in which four magnetoresistive elements are used for creating a magnetoresistive sensor according to one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] 1, a magnetoresistive sensor element 2 according to one embodiment comprises a ferromagnetic reference layer 23 with a pinned reference magnetization 230, a ferromagnetic sense layer 21 with a sense magnetization 210 movable in response to an external magnetic field 60, and a tunnel barrier layer 22 between the sense ferromagnetic layer 21 and the reference ferromagnetic layer 23. The sense magnetization 210 comprises a stable vortex configuration with a core 213 that is reversibly movable in response to the external magnetic field 60 (see Figures 2a and 2b).

[0020] The ferromagnetic layer may be made of an Fe-based alloy such as CoFe, NiFe, CoFeB. The reference layer can be pinned by an antiferromagnetic layer 24 through a magnetic exchange bias coupling. The antiferromagnetic layer can be Iridium (Ir) and Mn-based alloys (e.g., IrMn), Fe and Mn based alloys (e.g., FeMn); Platinum (Pt) and Mn-based alloys (e.g., PtMn) and It may include manganese Mn-based alloys, such as alloys based on Ni and Mn (eg, NiMn). 1, the reference layer 23 may include a synthetic antiferromagnet (SAF) comprising at least a first ferromagnetic layer 231 separated from a second ferromagnetic layer 232 by an antiparallel coupling layer 233. The antiparallel coupling layer 233 is a layer of Ru, Ir, Cu, or a combination of these elements. The second reference magnetization 235 of the ferromagnetic layer 232 next to the antiferromagnetic layer 24 is pinned, and the first reference magnetization 234 of the first ferromagnetic layer 231 is coupled antiparallel to the second reference magnetization 235 by the antiparallel coupling layer 233. The tunnel barrier (layer) 22 may contain an insulating material. Suitable insulating materials include oxides such as aluminum oxide (e.g., AI2O3) and magnesium oxide (e.g., MgO). The thickness of the tunnel barrier layer 22 may be in the nanometer nm range, such as about 1 nm to about 3 nm.

[0021] 7 shows details of the sense layer 21 according to one embodiment. The sense layer 21 comprises a first ferromagnetic sense portion 211 in contact with the tunnel barrier layer 22 and a second ferromagnetic sense portion 212 in contact with the first ferromagnetic sense portion 211. The second ferromagnetic sense part 212 comprises a dilution factor in such a proportion that the temperature dependence of the magnetic susceptibility χ of the sense layer 21 substantially compensates for the temperature dependence of the tunneling magnetoresistance TMR of the magnetoresistive sensor element 2. The second ferromagnetic sense part 212 must be thick enough (to suit the size of the device) to allow a vortex state.

[0022] The dilution element dilutes the sense magnetization 210 and lowers the Curie temperature Tc of the sense layer 21. s (T) / M s The saturation magnetization normalized by (0) is an undiluted sense magnetization (curve A) with a first Curie temperature TC1; First Curie temperature T c1 The second Curie temperature T is smaller than c2 A moderately diluted sense magnetization (curve B) with Second Curie temperature T c2 The third Curie temperature T is smaller than c3 A highly diluted sense magnetization (curve C) with 4 is shown as a function of temperature T for

[0023] In addition, Fig. 8 shows the operating temperature range T WR Also shown is the tangent at the midpoint of curves A to C in the operating temperature range T WR is shown by the dotted box in FIG. 8 and corresponds to the temperature at which the magnetoresistive sensor element 2 normally operates. Reducing the Curie temperature Tc of the sense layer 21 reduces the operating temperature range T WR The tangent line from curve A to curve C shows that as temperature T increases, the magnetization decreases more quickly. If the magnetization decreases more quickly with increasing temperature T, the magnetic susceptibility χ increases more quickly with increasing temperature.

[0024] By adjusting the dilution of the sense magnetization 210, it is possible to substantially compensate for the decrease in TMR that accompanies the increase in magnetic susceptibility χ with increasing temperature. Thus, by adjusting the dilution of the sense magnetization 210, it is possible to control the TCS, e.g., by adjusting the TCS over the operating temperature range T WR Here, dilution of the sense magnetization 210 is achieved by adding a dilution element to the ferromagnetic material forming the second ferromagnetic sense portion 212.

[0025] In one embodiment, the diluent element is a transition metal element. For example, the second ferromagnetic sense portion 212 may include a NiFe alloy containing a transition metal element. The transition element may include, for example, tantalum (Ta), tungsten (W), or ruthenium (Ru).

[0026] FIG. 9 reports the measured saturation magnetization normalized at room temperature IWM (RT) as a function of temperature T of the sense layer 21, where the second ferromagnetic sense portion 212 contains a NiFe alloy with different percentages of diluent elements contained in the layer. Magnetization curves are reported for no dilution (curve A), for a concentration of 10% vol of Ta (curve C), for a concentration of 10% vol of W (curve D) and for a concentration of 7% vol of Ta (curve B). FIG. 10 shows that the inclusion of Ta in the NiFe alloy of the second ferromagnetic sense portion 212 leads to a faster decrease in magnetization with temperature T. The addition of W to the second ferromagnetic sense portion 212 results in a stronger decrease in magnetization with temperature T than the addition of Ta.

[0027] 10 shows the TCS values ​​for various dilutions achieved by Ta addition in a NiFe alloy for a second ferromagnetic sense portion 212 having a vortex configuration of sense magnetization 210 with a diameter of about 440 nm. The TCS is substantially compensated (TCS approaches a null value) at a concentration of about 8% vol of Ta in the NiFe alloy.

[0028] 11, the second ferromagnetic sense portion 212 includes a plurality of ferromagnetic sublayers 214 containing a ferromagnetic alloy and a plurality of diluent sublayers 215 containing a diluent element, e.g., containing a transition metal element. The ferromagnetic sublayers 214 may have a thickness of 0.5 nm or more. For example, the ferromagnetic sublayers 214 may have a thickness between 0.5 and 5 nm. The diluent sublayers 215 may have a thickness between 0.1 and 0.5 nm.

[0029] The ferromagnetic sublayer 214 may include NiFe, CoFe, or CoFeB alloys.

[0030] The first ferromagnetic sense portion 211 may include a CoFeB alloy.

[0031] In one particular example, the first ferromagnetic sense portion 211 comprises a CoFeB alloy and the second ferromagnetic sense portion 212 comprises a plurality of ferromagnetic sublayers 214 containing a ferromagnetic NiFe alloy; and a plurality of dilute sublayers 215 containing Ta, where the first ferromagnetic sense portion 211 may have a thickness of about 2.4 nm, the ferromagnetic sublayers 214 may have a thickness of about 1.2 nm, and the dilute sublayers 215 may have a thickness of about 0.1 nm.

[0032] According to one embodiment, the method for manufacturing the magnetoresistive sensor element 2 comprises carrying out the following steps for a number of temperatures and concentrations of dilution elements: The electrical conductance G of the magnetoresistive sensor element 2 is compared with the magnetic field H for a number of temperatures T so as to obtain a number of measured conductance curves for each temperature T. ext Step 2: Measure as a function of Calculating the value of the TMR of the magnetoresistive sensor element 2 from the multiple measured conductance curves, such as to determine the temperature dependence of the TMR. Measuring the magnetization of the sense layer 21, such as to determine the temperature dependence of the magnetic susceptibility χ of the sense layer 21.

[0033] The electrical conductance G of the magnetoresistive sensor element 2 can be measured by passing a read current 31 (see FIG. 1) through the magnetoresistive sensor element 2. Examples of conductance curves measured at three different temperatures T are shown in FIGS. 6a to 6c.

[0034] From the preforming step, the method further comprises the step of determining a ratio of dilution factors at which the temperature dependence of the TMR substantially compensates for the temperature dependence of the magnetic susceptibility χ.

[0035] To compensate for TCS, the change in magnetization Ms(T) with temperature T is: Ms(T)=ATMR(T) / (2+TMR(T)) (3) where A is a constant, and in the case of the temperature dependence of TMR, it is TMR(T).

[0036] The magnetoresistive sensor for sensing a 1D external magnetic field Hext comprises a plurality of magnetoresistive sensor elements 2. In one embodiment shown in FIG. 12, the magnetoresistive sensor 20 is arranged in a Wheatstone full bridge configuration. This allows to improve the thermal stability and linearity of the sensor. Within such a full bridge, the diagonal elements 2 have the same response curve (e.g., FIG. 4a), and each half bridge has one sensing element with response curve 4a and another sensing element with an inverse response curve (FIG. 4b). This is achieved by having opposite orientations of the reference layer 230 for the two sense elements 2 with response curves like those of FIG. 4a and FIG. 4b, respectively.

[0037] The magnetoresistive sensor 20 detects V(V in =1V), the temperature dependence of TMR is given by the saturation magnetization F out This can be calculated from the electrical output Vout of the magnetoresistive sensor 20 in the hysteresis curve (see, for example, FIG. 3). TMR=2FB out / (FB out -2), Here, FB out =max(FB out )-min(FBout ) (4) Here, max(FB out ) and min(FB out ) is the saturation magnetization of the hysteresis loop.

[0038] The change in magnetization Ms(T) with temperature T is measured independently on the sense layer 21 using a magnetometer. It can be measured. The present application provides, for example, the following aspects: [Point 1] a reference layer (23) having a pinned reference magnetization (23); a sense layer (21) having a free sense magnetization (210) with a stable vortex configuration, the stable vortex configuration having a reversibly movable core (213); a tunnel barrier layer (22) between the reference layer (23) and the sense layer (22), the tunnel barrier layer (22) comprising an insulating material; In a magnetoresistive sensor element (2), the sense layer (21) comprises a first ferromagnetic sense portion (211) in contact with the tunnel barrier layer (22) and a second ferromagnetic sense portion (212) in contact with the first ferromagnetic sense portion (211); the second ferromagnetic sense portion (212) comprises a dilution element in such a way that the temperature dependence of the magnetic susceptibility (χ) of the sense layer (21) substantially compensates for the temperature dependence of the tunnel magnetoresistance (TMR) of the magnetoresistive sensor element (2); A magnetoresistive sensor element (2). [Point 2] The magnetoresistive sensor element (2) according to aspect 1, wherein the diluent element contains a transition metal element. [Point 3] The magnetoresistive sensor element (2) according to aspect 1 or 2, wherein the transition metal element contains Ta, W or Ru. [Point 4] The magnetoresistive sensor element (2) according to any one of the preceding aspects, wherein the first ferromagnetic sense portion (211) comprises a CoFeB alloy. [Point 5] The magnetoresistive sensor element (2) according to any one of the preceding aspects, wherein the second ferromagnetic sense portion (212) comprises a NiFe alloy containing said diluent element. [Point 6] A magnetoresistive sensor element (2) according to any one of aspects 1 to 5, wherein the second ferromagnetic sense portion (212) comprises a plurality of ferromagnetic sublayers (214) containing a ferromagnetic layer alloy and a plurality of dilution sublayers (215) comprising the dilution elements. [Point 7] A magnetoresistive sensor element (2) according to aspect 6, wherein each dilute sublayer (215) has a thickness between 0.1 nm and 0.5 nm and each ferromagnetic sublayer (214) has a thickness between 0.5 nm and 5 nm. [Point 8] The magnetoresistive sensor element (2) according to aspect 6 or 7, wherein the ferromagnetic sublayer (214) contains a NiFe alloy or a CoFe alloy or an alloy of CoFeB. [Point 9] A magnetoresistive sensor (20) for sensing a one-dimensional external magnetic field, comprising a plurality of magnetoresistive sensor elements (2) according to any one of the first to eighth aspects. [Point 10] 10. The magnetoresistive sensor (20) according to aspect 9, configured in a Wheatstone bridge configuration. [Point 11] A method for manufacturing a magnetoresistive sensor element (2) according to any one of the preceding aspects 1 to 8 for a number of temperatures (T) and different concentrations of dilution elements, comprising the steps of: measuring the electrical conductance (G) of the magnetoresistive sensor element (2) as a function of an external magnetic field (Hext) for a number of temperatures (T) such that a number of measured conductance curves for each temperature (T) are obtained; calculating a value of the TMR of the magnetoresistive sensor element (2) from the plurality of conductance curves, such as to determine a temperature dependence of the TMR; measuring the magnetization of the sense layer (21) to determine the temperature dependence of the magnetic susceptibility (χ) of the sense layer (21); determining a percentage of the diluent metal element such that the temperature dependence of the TMR substantially compensates for the temperature dependence of the magnetic susceptibility (χ); A method for manufacturing a magnetoresistive sensor element (2), comprising: [Explanation of symbols]

[0039] 2. Magnetoresistive sensor element 20 Magnetoresistive Sensor 21 Sensation Layer 210 Sense Magnetization 211 First ferromagnetic sense part 212 Second ferromagnetic sense part 213 Core 214 Ferromagnetic Sublayer 215 Dilution Sublayer 22 Tunnel Barrier Layer 23 Reference layer 230 Reference magnetization 231 First ferromagnetic layer 232 Second ferromagnetic layer 233 Antiparallel Coupled Layer 234 1st reference magnetization 235 Second reference magnetization 24 Antiferromagnetic layer 31 Read Current 60 External Magnetic Field G Electrical Conductance H ext External magnetic field H expl Emission magnetic field H nucl nucleation field Ms saturation magnetization S Sensitivity T temperature Tc Curie temperature TCS temperature sensitivity coefficient Tunnel Magnetoresistance (TMR) T WR Operating Temperature Range χ magnetic susceptibility

Claims

1. a reference layer having a pinned reference magnetization; a sense layer having a free sense magnetization with a stable vortex configuration, the stable vortex configuration having a reversibly movable core; a tunnel barrier layer between the reference layer and the sense layer, the tunnel barrier layer comprising an insulating material; A magnetoresistive sensor element comprising: the sense layer comprises a first ferromagnetic sense portion in contact with the tunnel barrier layer and a second ferromagnetic sense portion in contact with the first ferromagnetic sense portion; A magnetoresistive sensor element, wherein the second ferromagnetic sense portion comprises a dilution element in a proportion such that the temperature dependence of the magnetic susceptibility of the sense layer substantially compensates for the temperature dependence of a tunneling magnetoresistance (TMR) of the magnetoresistive sensor element.

2. A magnetoresistive sensor element as described in claim 1, wherein the dilution element contains a transition metal element.

3. The magnetoresistive sensor element of claim 2, wherein the transition metal element contains Ta, W or Ru.

4. The magnetoresistive sensor element of claim 1, wherein the first ferromagnetic sense portion contains a CoFeB alloy.

5. The magnetoresistive sensor element of claim 1, wherein the second ferromagnetic sense portion comprises a NiFe alloy containing the dilution element.

6. The magnetoresistive sensor element of claim 1, wherein the second ferromagnetic sense portion comprises a plurality of ferromagnetic sublayers containing a ferromagnetic layer alloy and a plurality of dilution sublayers comprising the dilution element.

7. 7. The magnetoresistive sensor element of claim 6, wherein each dilute sublayer has a thickness between 0.1 nm and 0.5 nm and each ferromagnetic sublayer has a thickness between 0.5 nm and 5 nm.

8. The magnetoresistive sensor element of claim 6, wherein the ferromagnetic sublayer comprises a NiFe alloy, a CoFe alloy, or a CoFeB alloy.

9. A magnetoresistive sensor for sensing a one-dimensional external magnetic field, comprising a plurality of magnetoresistive sensor elements, each of which comprises: a reference layer having a pinned reference magnetization; a sense layer having a free sense magnetization with a stable vortex configuration, the stable vortex configuration having a reversibly movable core; a tunnel barrier layer between the reference layer and the sense layer, the tunnel barrier layer comprising an insulating material; The magnetoresistive sensor element comprising: the sense layer comprises a first ferromagnetic sense portion in contact with the tunnel barrier layer and a second ferromagnetic sense portion in contact with the first ferromagnetic sense portion; A magnetoresistive sensor, wherein the second ferromagnetic sense portion comprises a dilution element in a proportion such that the temperature dependence of the magnetic susceptibility of the sense layer substantially compensates for the temperature dependence of the TMR of the magnetoresistive sensor element.

10. 10. The magnetoresistive sensor of claim 9 configured in a Wheatstone bridge configuration.

11. 1. A method for manufacturing a magnetoresistive sensor element, the magnetoresistive sensor element comprising: a reference layer having a pinned reference magnetization; a sense layer having a free sense magnetization with a stable vortex configuration, the stable vortex configuration having a reversibly movable core; a tunnel barrier layer between the reference layer and the sense layer, the tunnel barrier layer comprising an insulating material; The magnetoresistive sensor element comprising: the sense layer comprises a first ferromagnetic sense portion in contact with the tunnel barrier layer and a second ferromagnetic sense portion in contact with the first ferromagnetic sense portion; the second ferromagnetic sense portion comprises a dilution element in such a manner that the temperature dependence of the magnetic susceptibility of the sense layer substantially compensates for the temperature dependence of the TMR of the magnetoresistive sensor element; The method comprises the steps of: measuring the electrical conductance of the magnetoresistive sensor element as a function of an external magnetic field for a plurality of temperatures such that a plurality of measured conductance curves for each temperature are obtained; calculating a value of TMR of the magnetoresistive sensor element from a plurality of conductance curves, such as to determine a temperature dependence of TMR; measuring the magnetization of the sense layer to determine the temperature dependence of magnetic susceptibility of the sense layer; determining a proportion of said dilution element such that the temperature dependence of TMR substantially compensates for the temperature dependence of magnetic susceptibility; 1. A method for manufacturing a magnetoresistive sensor element, comprising:

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