Tunneling magnetoresistance (TMR) devices with improved seed layers.

Abstract

The present invention relates to a tunneling magnetoresistance (TMR) device having an improved seed layer for the bottom or first ferromagnetic layer that eliminates the need for boron in the two ferromagnetic layers. The seed layer, e.g., a RuAl alloy, when deposited on an amorphous pre-seed layer, has a B2 crystal structure with a (001) texture, meaning that the (001) plane is parallel to the surface of the TMR device substrate. The subsequently deposited first ferromagnetic layer, such as a CoFe alloy, and the tunnel barrier layer, which is typically MgO, inherit the (001) texture of the seed layer.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of U.S. Non-Provisional Application No. 17 / 472,019, entitled "TUNNELING MAGNETORESISTIVE (TMR) DEVICE WITH IMPROVED SEED LAYER," filed September 10, 2021, the entire contents of which are incorporated herein by reference for all purposes.

[0002] FIELD OF THE INVENTION The present invention relates generally to tunneling magnetoresistive (TMR) devices, and more particularly to TMR devices having seed layers that improve the formation of tunnel barrier layers and performance of TMR devices. [Background technology]

[0003] Description of Related Art Tunneling magnetoresistance (TMR) devices, also known as magnetic tunnel junction (MTJ) devices, consist of two ferromagnetic layers separated by a thin insulating tunnel barrier layer. The barrier layer is typically made of a metal oxide that is thin enough that quantum mechanical tunneling of charge carriers can occur between the two ferromagnetic layers. Various metal oxides have been proposed as tunnel barrier materials, including ZnO, MnO, CoO, TiO, and VO, but the most common material is crystalline magnesium oxide (MgO). The quantum mechanical tunneling process is electron spin dependent, meaning that the electrical resistance measured when applying a sense current across the junction depends on the spin-dependent electronic properties of the ferromagnetic and barrier layers and is a function of the relative orientations of the magnetizations of the two ferromagnetic layers.

[0004] In one type of TMR or MTJ device, called the pinned type, the magnetization of one ferromagnetic layer, called the reference layer, is fixed or pinned, and the magnetization of the other ferromagnetic layer, called the free layer, is free to rotate in response to an external magnetic field. Pinned TMR devices can be used in magnetic recording read / write heads, where the magnetization of the free ferromagnetic layer rotates relative to the magnetization of the reference ferromagnetic layer in the presence of a magnetic field from a recorded magnetic medium. Pinned TMR devices can also be used in magnetic random access memory (MRAM) devices (e.g., spin-transfer torque MRAM (STT-MRAM) and spin-orbit torque MRAM (SOT-MRAM)) that use MTJs as memory storage bits or cells, where the magnetization of the free layer relative to the reference layer in the MTJ is changed directly by current. TMR devices can also be used as part of magnetic sensor devices that can be used in a variety of applications (e.g., industrial, automotive, and medical).

[0005] In another type of TMR device, called the dual free layer (DFL) type, there are two free ferromagnetic layers whose magnetizations are free to rotate relative to each other in a "scissoring" effect in response to an external magnetic field. DFL read heads for magnetic recording devices are described in U.S. Patent Nos. 7,035,062 B2 and 8,670,217 B1. Summary of the Invention

[0006] TMR devices with MgO tunnel barrier layers, such as CoFe / MgO / CoFe tunnel junctions, exhibit very large tunnel magnetoresistance (TMR) due to the coherent tunneling of electrons with specific symmetries. However, the ferromagnetic layers and MgO barrier layers must be perfectly crystalline to achieve high TMR. Ferromagnetic layers and MgO barrier layers are typically formed by sputter deposition and subsequent annealing, which creates a crystalline structure. CoFe / MgO / CoFe tunnel junctions exhibiting the required low resistance-area area (RA) do not exhibit high TMR, likely due to the poor crystallinity of the MgO barrier layer. However, it has been found that when boron (B) is used in one or more ferromagnetic layers, such as using a thin amorphous CoFeB or CoFeBTa layer in a multilayer structure, higher TMR is observed after annealing. The amorphous CoFeB layer promotes better growth of MgO with a (001) texture (surface plane parallel to the surface of the substrate), thus promoting higher TMR.

[0007] Advanced TMR devices with even higher TMR require a reduction in the resistance-area product (RA), which means that the MgO barrier layer needs to be thinner. However, as the MgO thickness decreases, the breakdown voltage and TMR also decrease, which is believed to be due in part to the diffusion of boron into the MgO barrier layer. What is needed is a TMR device with a thin MgO barrier layer, thus reducing RA, but with high TMR.

[0008] Embodiments of the present invention relate to TMR devices with an improved seed layer for the bottom or first ferromagnetic layer that eliminates the need for boron in the ferromagnetic layer. The seed layer, e.g., a RuAl alloy, has a B2 crystal structure (also known as a CsCl crystal structure) with a (001) texture, meaning that the (001) plane is parallel to the surface of the TMR device substrate. The subsequently deposited first ferromagnetic layer, such as a CoFe alloy, and the tunnel barrier layer, typically MgO, also inherit the (001) texture of the seed layer. After deposition and annealing of the second ferromagnetic layer, the absence of diffused boron and the larger grain size of the boron-free ferromagnetic layer improves crystallization of the ferromagnetic layer and the tunnel barrier layer, thereby reducing defects at the grain boundaries. The resulting TMR device exhibits reduced RA and increased TMR compared to prior art boron-containing TMR devices.

[0009] For a fuller understanding of the nature and advantages of the present invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0010] [Figure 1] 1A-1C are cross-sectional views showing the structure of two types of conventional tunneling magnetoresistance (TMR) devices. [Figure 2] FIG. 1 is a perspective view of a magnetic tunnel junction (MTJ) as a memory cell in a spin-transfer torque magnetization reversal magnetic random access memory (STT-MRAM) device. [Figure 3] 1 is a cross-sectional view showing the detailed structure of a prior art pinned TMR read head. [Figure 4] FIG. 1 is a schematic diagram showing a typical ferromagnetic (FM1) / MgO / FM2 structure with boron present in both FM layers. [Figure 5] 1 is a schematic cross-sectional view of an FM1 layer / MgO / FM2 layer structure according to one embodiment of the present invention having an improved seed layer and boron-free FM1 and FM2 layers. [Figure 6A]FIG. 1 is a schematic side view illustrating the growth of a (001) textured FM1 and tunnel barrier layer on a B2 structure seed layer. [Figure 6B] Schematic top view of the (001) planes of the RuAl (seed), CoFe (FM1), and MgO (tunnel barrier) layers, showing the NaCl structure of the MgO layer with the (001) plane grown at a 45 degree angle on the CoFe layer. [Figure 7] 1 is a graph of measured TMR versus resistance area product (RA) for a prior art double free layer (DFL) device and a DFL device according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] FIG. 1 shows cross-sectional views of two types of TMR read heads 10. The TMR read head includes a bottom ferromagnetic (FM1) layer 18, an insulating tunnel barrier layer 20, and a top ferromagnetic (FM2) layer 32. The TMR read head has bottom and top non-magnetic electrodes or leads 12, 14, respectively, with the bottom non-magnetic electrode 12 formed on a suitable substrate. A seed layer (not shown) may be disposed between the bottom lead and FM1, and a cap layer (not shown) may be disposed between FM2 and the top lead. In a DFL read head, both FM1 and FM2 are "free" ferromagnetic layers because their magnetizations are free to rotate relative to each other by the scissoring effect in the presence of an external magnetic field from the recorded magnetic medium.

[0012] In a pinned TMR device, the magnetization of either FM1 or FM2 is fixed or pinned, while the magnetization of the other ferromagnetic layer is free to rotate in the presence of an external magnetic field. The pinned ferromagnetic layer is called the reference layer because its magnetization is prevented from rotating. The magnetization of the reference layer can be fixed or pinned by being formed from a high-coercivity film or by being exchange-coupled to an antiferromagnetic (AF) "pinning" layer. Pinned TMR devices can be used as memory cells in STT-MRAM devices, as shown in Figure 2. A single MTJ is shown in the STT-MRAM device. The magnetization orientation of the free ferromagnetic layer can be modified using a spin-polarized current to have either a parallel or antiparallel orientation relative to the fixed magnetization of the reference layer, thereby generating two resistance levels that represent a 1 (parallel) or a 0 (antiparallel) as a bit in the MTJ cell. MTJs can also be used in SOT-MRAM devices, which differ from STT-MRAM primarily in how writing is achieved by the SOT effect instead of the STT effect. As mentioned above, in addition to read head and magnetic memory applications, TMR devices can also be part of sensor devices.

[0013] Pinned TMR devices can also be used as read heads in magnetic recording devices such as hard disk drives, as shown in detail in FIG. 3. FIG. 3 is a highly schematic cross-sectional view illustrating the structure of a prior art pinned TMR read head such as that used in magnetic recording hard disk drives. This cross-sectional view is a view of what is commonly referred to as the gas bearing surface (GBS) of the TMR read head. The TMR read head includes a sensor stack of layers formed between two ferromagnetic shield layers S1, S2, typically made of electroplated NiFe alloy films. The sensor stack includes a ferromagnetic reference layer 120 with a pinned magnetization 121 oriented transversely (away from the page), a ferromagnetic free layer 110 with a magnetization 111 that can rotate within the plane of the layer 110 in response to a transverse external magnetic field from the recording disk, and an electrically insulating tunnel barrier layer 130, typically magnesium oxide (MgO), between the ferromagnetic reference layer 120 and the ferromagnetic free layer 110.

[0014] The reference layer 120 can be a conventional "simple" or single pinned layer whose magnetization direction 121 is pinned or fixed, typically by being exchange coupled to an antiferromagnetic layer. However, in the example of FIG. 3 , the reference layer 120 is part of a well-known antiparallel (AP) pinned or flux-closure structure, also called a "laminated" pinned layer, as described in U.S. Pat. No. 5,465,185. The AP pinned structure minimizes magnetostatic coupling between the reference layer 120 and the free layer 110. The AP pinned structure includes a reference ferromagnetic (AP2) layer 120 and a lower pinned ferromagnetic (AP1) layer 122 antiferromagnetically coupled across an AP-coupled (APC) layer 123, such as Ru, Ir, Rh, or Cr, or an alloy thereof. Due to the antiparallel coupling across the APC layer 123, the reference (AP2) ferromagnetic layer 120 and the pinned (AP1) ferromagnetic layer 122 have their respective magnetizations 121, 127 oriented antiparallel to each other. As a result, the net magnetization of the AP2 and AP1 ferromagnetic layers 120, 122 is so small that the demagnetization field induced by the flux closure structure in the ferromagnetic free layer 110 is substantially minimized, thus enabling the TMR read head to operate optimally.

[0015] Disposed between the substrate, the bottom shield layer S1, and the AP pinned structure are a seed layer 125 and an antiferromagnetic (AF) pinned layer 124. The seed layer 125 facilitates the growth of a microstructure with strong crystalline texture in the AF pinned layer 124, thereby exhibiting strong antiferromagnetism. Therefore, the AF pinned layer 124 is strongly exchange coupled to the ferromagnetic pinned layer 122, thereby tightly pinning the magnetization 127 of the ferromagnetic pinned layer 122 perpendicular to and away from the GBS. Antiparallel coupling across the APC layer 123 then strongly pins the magnetization 121 of the ferromagnetic reference layer 120 perpendicular to and toward the ABS, and antiparallel to the magnetization 127. As a result, the net magnetization of the ferromagnetic AP2 layer 120 and the AP1 layer 122 is strongly pinned, thereby ensuring optimal operation of the TMR read head.

[0016] A layer 112, sometimes called a capping layer or cap layer, is disposed between the ferromagnetic free layer 110 and the top shield layer S2. The layer 112 protects the ferromagnetic free layer 110 from chemical and mechanical damage during processing so that the ferromagnetic free layer 110 maintains good ferromagnetic properties.

[0017] In the presence of an external magnetic field within the range of interest, i.e., the magnetic field from data written on the recording disk, the net magnetization of the ferromagnetic layers 120, 122 remains tightly pinned, but the magnetization 111 of the ferromagnetic free layer 110 rotates in response to the magnetic field. Thus, the sense current I S When a sense current flows perpendicularly from the top shield layer S2 through the sensor stack to the bottom shield layer S1, the magnetization rotation of the ferromagnetic free layer 111 results in a change in the angle between the magnetization of the ferromagnetic reference layer 120 and the magnetization of the ferromagnetic free layer 110, which is detectable as a change in electrical resistance. Because the sense current is directed perpendicularly through the stack of layers between the two shields S1 and S2, the TMR read head is a current perpendicular to the plane (CPP) read head.

[0018] Figure 3 also shows optional separate electrical leads 126 and 113 between the shields S1 and S2, respectively, and the sensor stack. The leads are optional and may be used to adjust the spacing between the shields. If the leads 126 and 113 are not present, the bottom shield S1 and top shield S2 are used as electrical leads. The TMR read head shown in Figure 3 is a "bottom-pinned" read head because the AP pinned structure is below the free layer 110; however, the free layer 110 could be positioned below the AP pinned structure. In such a configuration, the layers of the AP pinned structure would be reversed, with the AP2 layer 120 above and in contact with the barrier layer 130.

[0019] MgO tunnel junctions are required to have a (001) texture and perfect crystallinity. The MgO barrier layer is typically deposited as a (001) textured NaCl (rock salt) crystalline structure on an amorphous layer by sputter deposition, and subsequent annealing improves the crystalline structure by removing strain. It has been shown that using a thin amorphous CoFeB or CoFeBTa layer for one or both ferromagnetic layers can result in higher TMR or TMR ratio (ΔR / R). The as-deposited amorphous CoFeB layer is known to promote (001) textured MgO and higher TMR with CoFeB crystallization to a (001) texture after annealing.

[0020] FIG. 4 is a schematic cross-sectional view of a typical FM1 / MgO / FM2 structure with boron present in both ferromagnetic layers. FM1 and FM2 can both be free layers in a DFL device, or one of FM1 and FM2 can be a reference layer in a pinned device. The reference and free ferromagnetic layers are each shown as a thin (e.g., about 1-4 Å thick) CoFe "nanolayer" adjacent to an MgO barrier layer, a CoFe layer, and a CoFeB (possibly CoHf, CoFeBTa, or other amorphous insertion layer) layer between the nanolayer and the CoFe layer. The CoFeB layer is (Co x Fe (100-x) ) (100-y) B ywhere the subscripts represent atomic percent, x is about 40-100, and y is about 10-20. The total thickness of each of the FM1 and FM2 ferromagnetic layers is typically about 20-80 Å. Other materials are known to be used for the ferromagnetic layers, such as Co or Fe nanolayers, NiFe alloys, and Heusler alloys.

[0021] However, in the prior art TMR device of Figure 4, it was discovered that boron diffuses into the MgO barrier layer during annealing, which reduces the breakdown voltage and TMR. Also, for advanced TMR devices, the MgO needs to be thinner to reduce the resistance-area product (RA). A thinner MgO barrier layer is more susceptible to boron diffusion. Also, the smaller grains of MgO deposited on CoFeB mean that there may be more defects at the MgO grain boundaries after annealing.

[0022] FIG. 5 is a schematic cross-sectional view of an FM1 / MgO / FM2 layer structure having a boron-free ferromagnetic layer and an improved seed layer according to one embodiment of the present invention. Each of the FM1 and FM2 layers may be a single layer or multiple layers. FM1 is shown with an optional Co (or CoFe) nanolayer adjacent to the MgO interface. A conductive amorphous pre-seed layer is deposited directly on a lead layer formed on a suitable substrate. The pre-seed layer may be a layer or multiple layers including a material selected from NiFeTa alloy, CoFeTa alloy, CoFeB alloy, CoFeBTa alloy, and Ta, with a total thickness in the range of approximately 5-50 Å. A conductive seed layer, preferably a RuAl alloy (or alternatively a CrMo alloy), is deposited directly on the pre-seed layer and is formed as a B2 crystal structure (also called a CsCl structure) in the case of RuAl, or as a BCC phase in the case of CrMo (Mo is approximately 30-50 atomic percent), with a (001) texture, i.e., the (001) plane is parallel to the surfaces of the pre-seed layer and the substrate. The RuAl seed layer has a thickness in the range of about 5-50 Å and Ru x Al (100-x)where x is an atomic percent and is greater than or equal to 45 and less than or equal to 60. A boron-free FM1 layer, preferably a CoFe alloy, is deposited on the seed layer, <001> The FM1 layer has a BCC structure and inherits the (001) texture. An optional BCC sublayer, such as Cr (not shown in Figure 5), can be deposited on the seed layer before the deposition of the FM1 layer; in this case, the FM1 layer is deposited directly on the sublayer. (As used herein, the phrase "on a layer" means that there may be one or more intermediate layers between the upper and lower layers, and the phrase "directly on a layer" means that the upper layer is directly on and in contact with the lower layer.) The boron-free FM1 layer has a typical thickness in the range of 20-80 Å and may be multilayered, as shown in Figure 5. While CoFe alloys are the preferred material for FM1, other suitable materials with a BCC structure that can inherit the (001) texture of the seed layer include CoFeNi-based alloys, Heusler alloys such as Co2MnSi, Co2MnAl, Co2MnGe, Co2FeSi, and Co2FeAl, and half-Heusler alloys such as NiMnSb. Next, an MgO barrier layer is deposited directly on the CoFe layer or on an optional Co nanolayer (2-20 Å) to a thickness in the range of approximately 4-20 Å. The MgO barrier layer is epitaxially grown on the FM1 layer with a 001 texture. While MgO is preferred, other materials that can function as a tunnel barrier layer and inherit the (001) texture of the FM1 layer include ZnO, MnO, CoO, TiO, and VO, as well as spinel materials such as MgAl2O4 and MgGa2O4. Figure 6A shows the structure of the FM1 and tunnel barrier layers with a (001) texture on a RuAl seed layer. <001> Figure 6B is a schematic side view showing the growth direction. Figure 6B is a schematic top view of the (001) planes of the RuAl (seed), CoFe (FM1), and MgO (tunnel barrier) layers, showing that the (001) plane of the NaCl structure of the MgO layer is at a 45 degree angle on the CoFe layer.

[0023] Next, the FM2 layer is deposited on the MgO barrier layer. The FM2 layer is also preferably boron-free and is preferably a CoFe alloy, but may contain B for soft magnetic properties and reduced magnetostriction. The FM2 layer may have a BCC structure or may be a multilayer including amorphous or FCC layers, provided that the layer at the MgO interface has a BCC structure. After deposition of the layers in the stack, the stack is preferably annealed at approximately 180-280°C for 2-5 hours. This improves the crystallinity of the FM1 and FM2 layers and the barrier layer by reducing strain. Unlike prior art, there is no boron diffusion into the barrier layer. Also, while defects in the crystalline structure of the barrier layer, which is typically MgO, are located at grain boundaries, the grains in the barrier layer in various embodiments of the present invention are larger than those in barrier layers formed on prior art CoFeB layers, resulting in fewer defects in the barrier layer after annealing. A nonmagnetic cap layer, such as a Ru / Ta / Ru multilayer, may be formed on FM2.

[0024] FIG. 7 is a graph of measured TMR versus R for a prior art DFL wafer (as in FIG. 4) and a DFL wafer according to one embodiment of the present invention (as in FIG. 5). The TMR ratio is given by ΔR / R=(R AP -R P ) / R P where R P and R AP represents the resistance measured for parallel and antiparallel configurations of ferromagnetic layer magnetization. The prior art DFL wafer, whose data is represented by the lower curve, had FM1 with a CoHf(20 Å) / CoFeB(50 Å) / Co(4 Å) multilayer and FM2 with a CoFe(4 Å) / CoFeB(50 Å) / CoHf(20 Å) multilayer. The embodiment of the present invention, whose data is represented by the upper curve, had a RuAl seed layer, FM1 with a CoFe(50 Å) / Co(5 Å) multilayer, and FM2 with a CoFe(50 Å) layer. The RA range was approximately 0.34-0.38 (ohm-micron). 2), embodiments of the present invention have a higher TMR of about 80-100% compared to the prior art, which has a range of about 50-85%. Similarly, for a TMR range of about 50-85%, embodiments of the present invention have a TMR of about 0.34-0.38 (ohm-micron). 2 ) range of about 0.28 to 0.34 (ohm-microns) compared to the prior art 2 ) have a lower RA.

[0025] While the present invention has been particularly shown and described with reference to preferred embodiments, it will be understood by those skilled in the art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Accordingly, the disclosed invention is to be considered merely as illustrative and limited only in scope as defined in the appended claims. The following items are elements that are claimed in the international application: (Item 1) A tunneling magnetoresistance (TMR) device, comprising: A substrate; a seed layer having a crystalline structure and a (001) texture on the substrate; a boron-free first ferromagnetic layer having a BCC crystal structure and a (001) texture on the seed layer, the first ferromagnetic layer being selected from a CoFe alloy, a Heusler alloy, and a half-Heusler alloy; a tunnel barrier layer having a rock salt crystal structure or a spinel structure and a (001) texture on the first ferromagnetic layer; a second ferromagnetic layer on the tunnel barrier layer; and A tunneling magnetoresistance (TMR) device comprising: (Item 2) Item 10. The device of item 1, wherein the seed layer is selected from RuAl alloys and CrMo alloys. (Item 3) The tunnel barrier layer is made of MgO, ZnO, MnO, CoO, TiO, VO, or MgAl 2 O 4 and MgGa 2 O 4 Item 1. The device according to item 1, selected from: (Item 4) Item 10. The device of item 1, further comprising an amorphous pre-seed layer between the substrate and the seed layer. (Item 5) Item 5. The device of item 4, wherein the pre-seed layer is a layer or multilayer comprising a material selected from NiFeTa alloys, CoFeTa alloys, CoFeB alloys, CoFeBTa alloys, and Ta. (Item 6) Item 10. The device of item 1, wherein the first ferromagnetic layer comprises a nanolayer selected from Co and CoFe alloys. (Item 7) Item 10. The device of item 1, further comprising a non-ferromagnetic sublayer having a BCC crystal structure between the seed layer and the first ferromagnetic layer. (Item 8) Item 8. The device of item 7, wherein the sublayer consists essentially of Cr. (Item 9) Item 10. The device of item 1, wherein the second ferromagnetic layer is a boron-free ferromagnetic layer. (Item 10) Item 1, wherein the TMR device is selected from a pinned TMR device and a double free layer (DFL) TMR device. (Item 11) Item 10. The device of item 1, wherein the TMR device is a magnetic recording read head. (Item 12) Item 12. A magnetic recording device comprising the magnetic recording read head of item 11. (Item 13) Item 1. A magnetic random access memory device comprising the TMR device of item 1. (Item 14) A sensor device comprising the TMR device according to item 1. (Item 15) A tunneling magnetoresistance (TMR) device, comprising: A substrate; an amorphous pre-seed layer on the substrate; a seed layer selected from a RuAl alloy and a CrMo alloy and having a crystalline structure and a (001) texture on the pre-seed layer; a boron-free alloy comprising a first ferromagnetic layer of Co and Fe having a BCC crystal structure and a (001) texture on the seed layer; a tunnel barrier layer consisting essentially of MgO on the first ferromagnetic layer; a second ferromagnetic layer on the tunnel barrier layer; and A tunneling magnetoresistance (TMR) device comprising: (Item 16) Item 16. The device of item 15, wherein the pre-seed layer is a layer or multilayer comprising a material selected from NiFeTa alloys, CoFeTa alloys, CoFeB alloys, CoFeBTa alloys, and Ta. (Item 17) Item 16. The device of item 15, wherein the seed layer consists essentially of RuxAl(100-x), where x is atomic percent and is greater than or equal to 45 and less than or equal to 60. (Item 18) Item 16. The device of item 15, wherein the first ferromagnetic layer comprises a nanolayer selected from Co and a CoFe alloy adjacent to the tunnel barrier layer, and the second ferromagnetic layer comprises a nanolayer selected from Co and a CoFe alloy adjacent to the tunnel barrier layer. (Item 19) Item 16. The device of item 15, further comprising a sublayer consisting essentially of Cr between the seed layer and the first ferromagnetic layer. (Item 20) Item 16. The device of item 15, wherein the second ferromagnetic layer is a boron-free ferromagnetic layer. (Item 21) Item 16. The device of item 15, wherein the TMR device is selected from a pinned TMR magnetic recording read head and a double free layer (DFL) magnetic recording read head. (Item 22) 22. A magnetic recording device comprising the magnetic recording read head of item 21. (Item 23) Item 16. The device of item 15, wherein the TMR device is a magnetic tunnel junction (MTJ) memory cell adapted for use in a magnetic random access memory (MRAM) device. (Item 24) 24. A magnetic random access memory device comprising the MTJ memory cell according to item 23. (Item 25) A sensor device comprising the TMR device according to item 1.

Claims

1. 1. A tunneling magnetoresistive (TMR) device comprising: A substrate; an amorphous pre-seed layer disposed on the substrate, the pre-seed layer being a layer or multilayer comprising a material selected from a NiFeTa alloy, a CoFeTa alloy, a CoFeB alloy, and a CoFeBTa alloy; a seed layer having a crystalline structure and a (001) texture on the pre-seed layer, the seed layer being selected from a RuAl alloy and a CrMo alloy; a boron-free first ferromagnetic layer having a BCC crystal structure and a (001) texture on the seed layer, the first ferromagnetic layer being selected from a CoFe alloy, a Heusler alloy, and a half-Heusler alloy; a tunnel barrier layer having a rock salt crystal structure or a spinel structure and a (001) texture on the first ferromagnetic layer; a second ferromagnetic layer on the tunnel barrier layer; and Equipped with A tunneling magnetoresistive (TMR) device, wherein the seed layer comprises the RuAl alloy, with an atomic percent of Ru between 45 and 60.

2. The tunnel barrier layer is made of MgO, ZnO, MnO, CoO, TiO, VO, or MgAl ２ O ４ and MgGa ２ O ４ The device of claim 1 , wherein the device is selected from:

3. The device of claim 1 , wherein the first ferromagnetic layer comprises a nanolayer selected from Co and CoFe alloys.

4. The device of claim 1 , wherein the second ferromagnetic layer is a boron-free ferromagnetic layer.

5. The first ferromagnetic layer is made of a CoFeNi-based alloy, Co ２ MnAl, Co ２ MnGe, Co ２ FeSi, Co ２ The device of claim 1 comprising FeAl or NiMnSb.

6. The device of claim 1 , wherein the seed layer has a thickness of 5 Å to 50 Å.

7. The device of claim 1 , wherein the first ferromagnetic layer has a thickness of 20 Å to 80 Å.

8. The device of claim 1 , wherein the tunnel barrier layer has a thickness of 4 Å to 20 Å.

9. The device of claim 1 , wherein the seed layer comprises the CrMo alloy with an atomic percent of Mo between 30 and 50.

10. 1. A tunneling magnetoresistive (TMR) device comprising: A substrate; an amorphous pre-seed layer on the substrate, the pre-seed layer being a layer or multilayer comprising a material selected from a NiFeTa alloy, a CoFeTa alloy, a CoFeB alloy, and a CoFeBTa alloy; a seed layer selected from a RuAl alloy and a CrMo alloy, the seed layer having a crystalline structure and a (001) texture on the pre-seed layer; a boron-free alloy comprising a first ferromagnetic layer of Co and Fe having a BCC crystal structure and a (001) texture on the seed layer; a tunnel barrier layer consisting essentially of MgO on the first ferromagnetic layer; a second ferromagnetic layer on the tunnel barrier layer; and Equipped with A tunneling magnetoresistive (TMR) device, wherein the seed layer consists essentially of Ru x Al (100-x), where x is atomic percent and is between 45 and 60 inclusive.

11. 11. The device of claim 10, wherein the first ferromagnetic layer comprises a nanolayer selected from Co and a CoFe alloy adjacent to the tunnel barrier layer, and the second ferromagnetic layer comprises a nanolayer selected from Co and a CoFe alloy adjacent to the tunnel barrier layer.

12. The device of claim 10 , wherein the second ferromagnetic layer is a boron-free ferromagnetic layer.

13. The device of claim 10 , wherein the seed layer has a thickness of 5 Å to 50 Å.

14. The device of claim 10 , wherein the first ferromagnetic layer has a thickness of 20 Å to 80 Å.

15. The device of claim 10 , wherein the tunnel barrier layer has a thickness of 4 Å to 20 Å.

16. The device of claim 10 , wherein the seed layer comprises the CrMo alloy with an atomic percent of Mo between 30 and 50.

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