Spin diode devices

Abstract

Spin diode device (100; 300; 500) configured to detect a microwave signal oscillating at a first target oscillation frequency or a second target oscillation frequency, the spin diode device (100; 300; 500) comprising: a magnetic tunnel contact stack (150) arranged between a lower electrode (130) and an upper electrode (140), the magnetic tunnel contact stack (150) comprising: a lower magnetic layer (102) with a lower magnetic film (312); a tunnel barrier layer (104) above the lower magnetic layer (102), wherein the tunnel barrier layer (104) comprises an insulating material; and an upper magnetic layer (106) above the tunnel barrier layer (104), wherein the upper magnetic layer (106) comprises an upper magnetic film (322); wherein each of the lower magnetic film (312) and the upper magnetic film (322) has a perpendicular magnetic anisotropy, wherein the lower magnetic film (312) comprises a first strength of perpendicular magnetic anisotropy corresponding to a first natural ferromagnetic resonance frequency, wherein the first natural ferromagnetic resonance frequency corresponds to the first target oscillation frequency, wherein the upper magnetic film (322) comprises a second strength of perpendicular magnetic anisotropy corresponding to a second natural ferromagnetic resonance frequency, wherein the second natural ferromagnetic resonance frequency corresponds to the second target oscillation frequency, where the second strength of perpendicular magnetic anisotropy differs from the first strength of perpendicular magnetic anisotropy, and where the second natural ferromagnetic resonance frequency differs from the first natural ferromagnetic resonance frequency.

Description

Technical field

[0001] Various embodiments relate to spin diode devices that include a magnetic tunnel contact. background

[0002] There is a growing need for microwave detection devices capable of detecting low-power microwaves. Existing solutions, such as spin diodes, typically exhibit poor performance in detecting low-power microwaves. To improve the performance of spin diodes for low-power operation, external energy is usually required to induce resonance in the magnetic tunnel contact layers of the spin diodes. However, because the spin diodes require an external energy source, the overall device becomes larger and its lifespan is limited. Furthermore, existing spin diodes can only utilize microwaves with a single frequency bandwidth. Therefore, to utilize microwaves with multiple frequency bandwidths, multiple spin diodes are required.

[0003] Document US 2019 / 0051822A1 discloses a synthetic antiferromagnetic layer comprising: a first ferromagnetic layer containing an amorphizing element, wherein the first ferromagnetic layer has a first structural symmetry;a second ferromagnetic layer with a second structural symmetry, wherein the first and second ferromagnetic layers are antiferromagnetically coupled by a trifunctional non-magnetic multilayer structure, wherein the antiferromagnetic coupling is an RKKY coupling, and the non-magnetic multilayer structure comprises at least two non-magnetic layers, and the non-magnetic multilayer structure is at least partially nanocrystalline or amorphous to ensure a structural transition between the first ferromagnetic layer with the first structural symmetry and the second ferromagnetic layer with the second structural symmetry, and the non-magnetic multilayer structure is capable of absorbing at least some part of the amorphizing element from the first ferromagnetic layer in contact with the non-magnetic multilayer structure.

[0004] US Patent 5,750,270 A discloses a magnetic recording medium comprising a substrate on which a nucleation layer of a non-magnetic metal selected from the group consisting of palladium or platinum, with a thickness greater than 50 nm, is deposited. The recording medium further comprises a recording layer consisting of a plurality of double layers of a magnetic metal or an alloy thereof with perpendicular magnetic anisotropy and a first thickness, and a non-magnetic metal selected from the group consisting of palladium or platinum, with a second thickness, and a retaining layer with a third thickness, the retaining layer being arranged between the nucleation layer and the substrate.The thickness of the nucleation layer, the first thickness, the second thickness and the number of double layers are chosen such that the medium has a coercive field strength of more than about 1000 Oe, where one Oe corresponds to approximately 79.5775 A / m, a signal output of more than 54 mV, a signal noise level of less than 44 mV and a signal-to-noise ratio of more than 7 dBm.

[0005] From US patent 2018 / 0248110A1, a magnetic device is known, comprising a first synthetic antiferromagnetic structure in a first plane, wherein the first synthetic antiferromagnetic structure includes a magnetic reference layer, the magnetic reference layer having a magnetization vector perpendicular to the first plane and having a fixed magnetization direction; a non-magnetic tunnel barrier layer in a second plane arranged above the magnetic reference layer; and a free magnetic layer in a third plane arranged above the non-magnetic tunnel barrier layer, the free magnetic layer having a magnetization vector perpendicular to the third plane and having a magnetization direction that can precess from a first magnetization direction to a second magnetization direction.the non-magnetic tunnel barrier layer and the free magnetic layer form a magnetic tunnel junction, a non-magnetic spacer layer in a fourth plane arranged above the free magnetic layer, the magnetic coupling layer comprising MgO, a magnetic precession spin current structure in a fifth plane physically separated from the free magnetic layer and coupled to the free magnetic layer by the non-magnetic spacer layer, the magnetic precession spin current structure having a magnetization vector with a magnetization direction in the fifth plane that can rotate freely in any magnetic direction in the fifth plane, the magnetic precession spin current structure comprising a first ferromagnetic precession spin current layer, a non-magnetic precession spin current insertion layer, and a second ferromagnetic precession spin current layer.wherein the first ferromagnetic precession spin current layer is arranged above the non-magnetic spacer layer, the non-magnetic precession spin current insertion layer is arranged above the first ferromagnetic precession spin current layer, and the second ferromagnetic precession spin current layer is arranged above the non-magnetic precession spin current insertion layer, and a cover layer in a sixth plane is arranged above the magnetic precession spin current structure. Electrons of an electric current flowing through the magnetic precession spin current structure are aligned in the magnetic direction of the magnetic precession spin current layer and are injected into the non-magnetic spacer, the free magnetic layer, the non-magnetic tunnel barrier layer, and the magnetic reference layer. The magnetization direction of the magnetic precession spin current structure precesses,which causes a spin transfer torque that assists in switching the magnetization vector of the free magnetic layer.

[0006] According to US patent 2019 / 0165255A1, a storage device is known that comprises a plurality of layers forming a stack, wherein the plurality of layers includes: a spin polarization layer with a magnetic anisotropy approximately perpendicular to a plane of the spin polarization layer, an antiferromagnetic layer comprising an antiferromagnetic material, a ferromagnetic layer exchange-coupled with the antiferromagnetic layer, the antiferromagnetic layer being located between the ferromagnetic layer and the spin polarization layer, and a storage layer with a magnetization direction indicating a storage state of the storage layer, the storage state being configured to be switched by a current through the stack.The spin polarization layer, the ferromagnetic layer, and the antiferromagnetic layer are configured to reduce the amount of current through the stack for switching the magnetization direction of the storage layer compared to the amount of current through a storage device without the spin polarization layer, the ferromagnetic layer, and the antiferromagnetic layer. Summary

[0007] According to various embodiments, a spin diode device is provided according to independent claim 1, wherein advantageous embodiments thereof are defined in dependent claims 2 to 17. Brief description of the drawings

[0008] In the drawings, identical reference numerals generally refer to identical parts in the different views. The drawings are not necessarily to scale, with the focus generally being on illustrating the principles of the invention. The following description details various embodiments with reference to the following drawings, in which: Fig. Figure 1 shows a schematic diagram of a spin diode device according to various non-limiting embodiments. Fig. Figure 2 shows a schematic diagram of an MTJ stack and the operating principle of the spin diode device of Fig. 1 represents. Fig. Figure 3 shows a schematic diagram of a spin diode device 300 according to various non-limiting embodiments. Fig. Figure 4 shows a schematic diagram of an MTJ stack and the operating principle of the spin diode device. Fig. 3 represents. Fig. Figure 5 shows a schematic diagram of the spin diode device according to various non-limiting embodiments. Fig. Figure 6 shows a schematic diagram of an MTJ stack and the operating principle of the spin diode device of Fig. 5 represents. Fig. Figure 7 shows an electrical circuit diagram of a microwave device according to various non-limiting embodiments. Fig. Figure 8 shows an electrical circuit diagram of a microwave device according to various non-limiting embodiments. Description

[0009] The embodiments generally relate to spin diode devices that include magnetic tunnel contacts. These spin diode devices can be spintronic devices. They can be used in applications such as WiFi energy harvesting, embedded object sensors, microwave imaging for medical or non-destructive testing, and microwave sensors in military applications.

[0010] Fig. Figure 1 shows a schematic diagram of a spin diode device 100 according to various non-limiting embodiments. The spin diode device 100 can comprise a lower electrode 130 and an upper electrode 140. The spin diode device 100 can include a magnetic tunnel contact stack (MTJ stack) 150 arranged between the lower and upper electrodes 130 and 140. The MTJ stack 150 can comprise three general layers, namely a lower magnetic layer 102, an upper magnetic layer 106, and a tunnel barrier layer 104 arranged between the lower magnetic layer 102 and the upper magnetic layer 106.

[0011] The lower magnetic layer 102 can be arranged above the lower electrode 130. The tunnel barrier layer 104 can be arranged above the lower magnetic layer 102. The upper magnetic layer 106 can be arranged above the tunnel barrier layer 104. The tunnel barrier layer 104 can separate the lower magnetic layer 102 from the upper magnetic layer 106. The tunnel barrier layer 104 can be non-magnetic and magnetically decouple the lower magnetic layer 102 from the upper magnetic layer 106. The upper electrode 140 can be arranged above the upper magnetic layer 106. The lower magnetic layer 102 and the upper magnetic layer 106 can each comprise at least one magnetic film exhibiting perpendicular magnetic anisotropy (PMA).

[0012] The tunnel barrier layer 104 can comprise magnesium oxide. In alternative embodiments, the tunnel barrier layer 104 can comprise aluminum oxide or other materials suitable for magnetically decoupling the layers above from the layers below. According to various non-limiting embodiments, the thickness of the tunnel barrier layer 104 can be from about 0.8 nm to about 2.0 nm. The tunnel barrier layer 104 can be sufficiently thin to allow electrons to tunnel through the tunnel barrier layer 104 from the upper magnetic layer 106 to the lower magnetic layer 102 or vice versa.

[0013] According to various non-limiting embodiments, the lower and upper electrodes 130, 140 can each comprise tantalum. Each of the lower and upper electrodes 130, 140 can be approximately 5 nm thick.

[0014] According to various non-limiting embodiments, the lower magnetic layer 102 and the upper magnetic layer 106 can each comprise a magnetic film with PMA. For example, the lower magnetic layer 102 can comprise a lower magnetic film (in Fig. 1 not shown) with a magnetization direction 152 in equilibrium that is perpendicular to a plane defined by the lower magnetic layer 102. For example, the upper magnetic layer 106 can similarly comprise an upper magnetic film (in Fig. (1 not shown) have a magnetization direction 156 in equilibrium that is perpendicular to a plane defined by the upper magnetic layer 106. The magnetization direction 152 of the lower magnetic layer 102 can be opposite to the magnetization direction 156 of the upper magnetic layer 106, i.e., antiparallel.

[0015] Fig. Figure 2 shows a schematic representation of the MTJ stack 150 and illustrates the operating principle of the spin diode device 100. The lower magnetic layer 102, in particular the lower magnetic film in the lower magnetic layer 102, can be structured to generate a natural ferromagnetic resonance frequency (FMR) f L to exhibit. The upper magnetic layer 106, in particular the upper magnetic film in the upper magnetic layer 106, can be structured to exhibit a natural FMR f U to exhibit. The natural FMR frequency of a magnetic film refers to the frequency at which the incident microwave radiation and the precession of the magnetization within a magnetic film couple in the absence of an external magnetic field.

[0016] In the presence of microwaves operating at frequency f LIf the lower magnetic layer 102 oscillates, it can absorb the microwave energy instead of the upper magnetic layer 106. The absorbed microwave energy can excite the magnetic moment in the lower magnetic film of the lower magnetic layer 102 to FMR. As a result, the magnetization direction of the lower magnetic layer 102 can change, for example, from the perpendicular direction 152 to a new direction 112. The new direction 112 can include a component 114 lying in the plane. The change in direction from the perpendicular direction 152 to the new direction 112 can be a slight displacement, such that the new direction 112 is closer to the perpendicular direction 152 than to a direction lying in the plane.

[0017] The magnetization direction of the upper magnetic layer 106 can remain relatively unchanged compared to that of the lower magnetic layer 102. Changing the magnetization direction of the lower magnetic layer 102 relative to the magnetization direction of the upper magnetic layer 106 can cause a change in the effective resistance across the MTJ stack 150, resulting in a rectification effect across the MTJ stack 150. This change in effective resistance across the MTJ stack 150 can alter the magnitude and / or direction of an electric current flowing between the lower electrode 130 and the upper electrode 140. The spin diode device 100 can detect microwaves based on the magnitude of the electric current, the direction of the electric current, or a combination thereof.

[0018] On the other hand, the upper magnetic layer 106 can absorb significantly more microwave energy than the lower magnetic layer 102 when the microwaves incident on the spin diode device 100 have a frequency of f Uoscillate. The absorbed microwave energy can excite electrons in the upper magnetic film of the upper magnetic layer 106 to FMR. As a result, the magnetization direction of the upper magnetic layer 106 can change, for example, from the perpendicular direction 156 to a new direction 122. The new direction 122 can include an in-plane component 124. The magnetization direction of the lower magnetic layer 102 can remain relatively unchanged compared to that of the upper magnetic layer 106. The change in the magnetization direction of the lower magnetic layer 102 relative to the magnetization direction of the upper magnetic layer 106 can cause a change in the effective resistance across the MTJ stack 150, resulting in a rectification effect across the MTJ stack 150.Changing the effective resistance across the MTJ stack 150 can alter the magnitude and / or direction of an electric current flowing between the lower electrode 130 and the upper electrode 140. The spin diode device 100 can detect the microwave based on the magnitude of the electric current, the direction of the electric current, or a combination thereof.

[0019] Furthermore, the change in the effective resistance of the MTJ stack 150 caused by a change in the magnetization direction of the upper magnetic layer 106 can differ from the change in the effective resistance of the MTJ stack 150 caused by a change in the magnetization direction of the lower magnetic layer 102. As such, the spin diode device 100 can also determine the oscillation frequency of the microwave based on the magnitude and direction of the electric current flowing between the lower electrode 130 and the upper electrode 140.

[0020] While Fig. Figure 2 shows that the magnetization directions of the lower magnetic layer 102 and the upper magnetic layer 106 are opposite to each other, i.e., antiparallel; in alternative embodiments, the lower magnetic layer 102 and the upper magnetic layer 106 can have the same magnetization direction.

[0021] Fig. Figure 3 shows a schematic diagram of a spin diode device 300 according to various non-limiting embodiments.

[0022] The lower magnetic layer 102 can comprise a lower magnetic film 312. The lower magnetic layer 102 can further comprise a lower coupling layer 314 arranged above the lower magnetic film 312, and another lower magnetic film 316 arranged above the lower coupling layer 314.

[0023] The lower magnetic film 312 and the further lower magnetic film 316 can each comprise cobalt, platinum, and combinations thereof. In alternative embodiments, the lower magnetic film 312 and the further lower magnetic film 316 can comprise various combinations of nickel, terbium, palladium, iron, boron, or other metals, or combinations thereof. The various elements in the lower magnetic film 312 and the further lower magnetic film 316 can be alloyed or formed from successive layers, so that in some embodiments the lower magnetic film 312 and the further lower magnetic film 316 can independently comprise a plurality of sublayers.The magnetic properties of the combined lower magnetic film 312 and the further lower magnetic film 316 can correspond to the magnetic properties of the lower magnetic layer 102 in embodiments with only two magnetic films in the lower magnetic layer 102. The lower magnetic film 312 and the further lower magnetic film 316 can comprise pinned layers.

[0024] According to various non-limiting embodiments, both the lower magnetic film 312 and the further lower magnetic film 316 can comprise at least one two-layer film, for example, a cobalt film arranged above or below another platinum film, for example, a Co / Pt film. The lower magnetic film 312 can comprise a plurality of two-layer films successively arranged in a stack. The lower magnetic film 312 can, for example, comprise up to six of these two-layer films, in particular [Co / Pt]6. The further lower magnetic film 316 can, for example, comprise up to four of these two-layer films, i.e., [Co / Pt]4. The number of required repetitions of the two-layer films can depend on the target microwave frequencies. In general, the higher the target microwave frequencies, the more two-layer films are required.

[0025] Each of the lower magnetic films 312, 316 can be magnetically anisotropic and exhibit PMA. The FMR frequency f L The thickness of the lower magnetic layer 102 can depend on the thicknesses of the cobalt film and the platinum film. For example, the thickness of the cobalt film and the platinum film can each be about 0.2 to 0.5 nm for an operating frequency range of about 20 GHz to about 60 GHz. In an exemplary embodiment, the two-layer film stack can comprise 0.4 nm of cobalt and 0.4 nm of platinum.

[0026] The lower coupling layer 314 can be an interlayer exchange coupling layer that facilitates antiferromagnetic exchange between the lower magnetic film 312 and the further lower magnetic film 316. This antiferromagnetic exchange can help reduce or compensate for magnetic stray field effects from the lower magnetic film 312 and the further lower magnetic film 316. The lower coupling layer 314 can cause the magnetization directions of the lower magnetic film 312 and the further lower magnetic film 316 to be antiparallel. Due to these opposing magnetization directions, the lower magnetic film 312 and the further lower magnetic film 316 can resonate at different frequencies and thereby absorb microwaves with different frequency bandwidths. The lower coupling layer 314 can comprise ruthenium (Ru), iridium (Ir), rhodium (Rh), or other materials.In various non-limiting embodiments, the lower coupling layer 314 can comprise ruthenium in a proportion of about 50 to about 100 wt. percent or about 80 to 100 wt. percent, based on the total wt. The thickness of the lower coupling layer 314 can be about 0.3 nm to 0.9 nm.

[0027] The upper magnetic layer 106 can overlay the tunnel barrier layer 104. The upper magnetic layer 106 can comprise an upper magnetic film 322. The upper magnetic layer 106 can further comprise a separating layer 324 over the upper magnetic film 322 and another upper magnetic film 326 over the separating layer 324. The upper magnetic film 322 and the other upper magnetic film 326 can comprise pinned layers. For example, the upper magnetic film 322 can comprise at least one pinned layer, and the other upper magnetic film 326 can also comprise at least one pinned layer. The upper magnetic films 322 and 326 can have the same or different compositions, and there can be more, fewer, or the same number of pinned layers in the upper magnetic films 322 and 326.The elements in the upper magnetic films 322, 326 can be present as alloys or as layers of a pure material or as layers of alloys. The upper magnetic films 322, 326 can comprise cobalt, iron, boron, alloys thereof, or mixtures thereof. For example, each of the upper magnetic films 322, 326 can be a cobalt-iron-boron alloy, such as Co. 20 Fe 60 B 20 The upper magnetic films 322, 326 can be magnetically “soft,” so that their spin-transfer torque and magnetization directions can be variable. Each of the upper magnetic films 322, 326 can be magnetically anisotropic and contain PMA. The thickness of the upper magnetic films 322, 326 can each be approximately 0.3 nm to approximately 1.2 nm.

[0028] The separating layer 324 can be arranged between the upper magnetic film 322 and the further upper magnetic film 326. The separating layer 324 can be non-magnetic. The separating layer 324 can provide ferromagnetic coupling between the upper magnetic films 322 and 326 and can be thin enough to be amorphous. In alternative embodiments, the separating layer 324 can be crystalline. The separating layer 324 can comprise tantalum, molybdenum, tungsten, iron, or other components in the form of alloys or individual elements. According to various non-limiting embodiments, the separating layer 324 can be approximately 0.4 nm thick.

[0029] The thicknesses of the lower magnetic films 312, 316 and the upper magnetic films 322, 326 can be crucial for achieving PMA and directly influence the natural FMR frequencies of these magnetic layers. The natural FMR frequencies of these magnetic films can determine the operating frequencies of the spin diode device 300. The spin diode device 300 can be configured to detect microwaves oscillating at frequencies that are identical to or correspond to the natural FMR frequencies of the lower magnetic films 312, 316. The spin diode device 300 can also be configured to detect microwaves oscillating at frequencies that are identical to or correspond to the natural FMR frequencies of the upper magnetic films 322, 326.

[0030] In general, the FMR frequency f of a magnetic film can be determined as follows: f=γ(Hext+4πMeff) where γ represents the gyromagnetic coefficient of the magnetic film material, H ext the strength of the external magnetic field and M eff represent the effective PMA strength of the magnetic film. M eff indicates the amount of extreme energy required to rotate the magnetization direction of the magnetic film from the vertical into the plane.

[0031] The spin diode device 100 can be operated without requiring an external magnetic field and consequently H ext = 0. The natural FMR frequencies of magnetic films can be expressed as follows: f=4πγMeff

[0032] In other words, the FMR frequency of the respective magnetic films can be adjusted to M effThe magnetic film strength (PMA) is directly proportional to the surface effect and the bulk effect. The surface effect can be caused by orbital deformation due to refractive periodicity at an interface. The bulk effect can be caused by orbital deformation due to the spatial asymmetry of the crystal. At an interface of a magnetic film, an electron can possess additional magnetic energy due to spin-orbit interactions. This additional energy can be so large that the direction of magnetization of the magnetic film at equilibrium is perpendicular to the plane, i.e., outside the plane. The PMA strength of a magnetic film can depend on the thickness of the magnetic film, its composition, the crystal structure, and the layers adjacent to the magnetic film.

[0033] For example, the thickness of the lower magnetic films 312, 316 can be in a range of about 2 nm to about 10 nm to achieve PMA with a natural FMR frequency and thus an operating frequency in the range of about 5 GHz to about 40 GHz. For example, the thickness of the upper magnetic films 322, 326 can be in a range of about 1.5 nm to about 3.0 nm to achieve PMA with a natural FMR frequency and thus an operating frequency in the range of about 1.5 GHz to about 20 GHz. For example, the thickness of the upper magnetic films 322, 326 can be in a range of about 0.4 nm to about 2.0 nm to achieve PMA with a natural FMR frequency and thus an operating frequency in the range of about 2 GHz to about 5 GHz.

[0034] The MTJ stack 150 can also include a seed layer 310. The seed layer 310 can be superimposed on the lower electrode 130. The seed layer 310 can be located beneath the lower magnetic layer 102 and also beneath the lower magnetic film 312. The seed layer 310 can comprise platinum. In various embodiments, the seed layer 310 can also comprise nickel, chromium, ruthenium, tungsten, magnesium, holmium, or terbium. The thickness of the seed layer 310 can be approximately 5 nm. The thickness and material of the seed layer 310 need not be limited to the thickness mentioned above, as long as the seed layer 310 is capable of forming a crystallized template for the lower magnetic film 312.

[0035] The MTJ stack 150 may further comprise a transition layer 318. The transition layer 318 may be arranged above the lower magnetic layer 102. The transition layer 318 may overlay the further lower magnetic film 316 if it is present in the lower magnetic layer 102. The transition layer 318 may be non-magnetic. In some embodiments, the transition layer 318 may comprise tantalum, iron, tungsten, molybdenum, terbium, cobalt, or other elements, either as alloys or as one or more pinned layers. The transition layer 318 may serve to separate the crystalline structure from the underlying further lower magnetic film 316 (or another pinned layer if more than two pinned layers are used). In some embodiments, the transition layer 318 may be amorphous. The transition layer 318 can be sufficiently thin so that no crystalline structure is formed, e.g.The transition layer 318 can be approximately 0.2 nm to 0.5 nm thick. The transition layer 318 can be non-magnetic, and its amorphous nature can even enable this non-magnetic property in embodiments that include iron, cobalt, or other materials that are normally magnetic.

[0036] The MTJ stack 150 may further comprise a polarizer layer 320. The polarizer layer 320 may superimpose the transition layer 318. The polarizer layer 320 may be magnetic. The polarizer layer 320 may comprise cobalt, iron, boron, alloys thereof, or combinations thereof, which may be present as alloys or as individual components and which, in various embodiments, may be present as a single layer or as multiple layers. The polarizer layer 320 may have a crystalline structure, which in some embodiments is imparted to the overlying layers and may improve the efficiency of spin polarization in the MTJ stack 150. The polarizer layer 320 may have a face-centered cubic crystalline structure, but other types of crystalline structures are also possible.

[0037] The MTJ stack 150 can further comprise a cover layer 330. The cover layer 330 can be arranged over the upper magnetic layer 106. The MTJ stack 150 can further comprise an optional upper barrier layer 328 arranged over the upper magnetic layer 106. The cover layer 330 can superimpose the optional upper barrier layer 328 where the upper barrier layer 328 is present. Thus, in embodiments in which the upper barrier layer 328 is present, the upper magnetic layer 106 can be interposed between the tunnel barrier layer 104 and the upper barrier layer 328. The upper electrode 140 can superimpose the cover layer 330. The cover layer 330 can further enhance the magnetic anisotropic effect of the MTJ stack 150.The top layer 330 can comprise one or more of the following materials: tungsten, magnesium oxide, ruthenium, platinum, hafnium, nickel-chromium, or other materials, either as alloys or as elements. The top layer 330 can be non-magnetic, and its composition can depend on the material of the upper magnetic films 322, 326. The optional upper barrier layer 328 can, in some embodiments, comprise magnesium oxide, and the upper barrier layer 328 can be non-magnetic. The top layer 330 can have a thickness of about 0.2 nm to about 2.0 nm. The upper barrier layer 328 can be about 1 nm thick.

[0038] According to various non-limiting embodiments, the spin diode device 300 can be manufactured using the same production line and processes as for the manufacture of MRAM devices. The lower magnetic layer 102 can comprise a synthetic antiferromagnet (SAF), so that it can be a solid layer. The upper magnetic layer 106 can be a free layer.

[0039] According to a non-limiting exemplary embodiment, the composition and thicknesses of each individual layer of the spin diode device 300 are described below. Each of the lower and upper electrodes 130, 140 can be about 5 nm thick and comprise tantalum. The seed layer 310 can be about 5 nm thick and comprise platinum. The lower magnetic film 312 can comprise six repetitions of a two-layer film of 0.4 nm cobalt and 0.4 nm platinum. The lower coupling layer 314 can be about 0.4 nm thick and comprise ruthenium. The further lower magnetic film 316 can comprise four repetitions of the two-layer film of 0.4 nm cobalt and 0.4 nm platinum. The transition layer 318 can be about 0.4 nm thick and comprise tantalum. The polarizer layer 320 can be about 1.0 nm thick and comprise cobalt. 20 Fe 60 B 20The tunnel barrier layer 104 can have a thickness of approximately 1.0 nm and comprise magnesium oxide. The upper magnetic film 322 can be approximately 1.2 nm thick and comprise Co 20 Fe 60 B 20 The separating layer 324 can be approximately 0.4 nm thick and comprise tantalum. The further upper magnetic film 326 can be approximately 0.9 nm thick and comprise co 20 Fe 60 B 20 The upper barrier layer 328 can be approximately 1.0 nm thick and comprise magnesium oxide. The cover layer 330 can be approximately 1 nm thick and comprise tungsten.

[0040] Fig. Figure 4 shows a schematic representation of the MTJ stack 150 and illustrates the operating principle of the spin diode device 300. Fig. 3. In the Fig. In the embodiment shown in Figure 3, the lower magnetic layer 102 comprises two lower magnetic films 312 and 316 separated by a lower coupling layer 314. The magnetization directions of the lower magnetic film 312 and the further lower magnetic film 316 can be antiparallel, and these lower magnetic films 312 and 316 can have different natural FMR frequencies. For example, the natural FMR frequency of the lower magnetic film 312 can be... L1 be, while the natural FMR frequency corresponds to the further lower magnetic film 316 f L2The magnetization directions of the upper magnetic film 322 and the further upper magnetic film 326 can be the same due to the interlayer exchange coupling effect mediated by the thickness and material choice of the coupling layer 524. Therefore, the upper magnetic films 322 and 326 can be treated as a single unit with a single natural FMR frequency f U The spin diode device 300 can be configured to detect microwaves emitted according to one of the frequencies f L1 , f L2 or f U oscillate. In other words, the spin diode device can detect 300 microwaves at three different frequencies. If the incident microwaves have a frequency of f UIf the incident microwaves have a frequency of f L1 If the incident microwaves have a frequency of f L2 According to the description, only the lower magnetic film 316 enters the FMR. Fig. 2. The effective resistance of the MTJ 150 changes when one of the magnetic films resonates, creating a rectifying effect in the spin diode device 300, which enables the spin diode device 300 to detect the microwave.

[0041] Fig. Figure 5 shows a schematic diagram of the spin diode device 500 according to various, non-limiting embodiments. The in Fig. The spin diode device 500 shown in section 5 can be used in the following diagram: Fig. The spin diode device 300 shown in Figure 3 may be similar, except that the separating layer 324 is replaced by an upper coupling layer 524. The upper coupling layer 524 may function similarly to the lower coupling layer 314. The upper coupling layer 524 may also be an interlayer exchange coupling layer and may serve to maintain antiparallel magnetization directions for the upper magnetic film 322 and the further upper magnetic film 326. Due to the antiparallel magnetization direction of the upper magnetic film 322 and the further upper magnetic film 326, as well as the lower magnetic film 312 and the further lower magnetic film 316, the spin diode device 100 may be configured to detect microwaves of four different frequencies. In the spin diode device 500, both the upper and lower magnetic layers 102 and 106 may comprise SAF.Both the upper coupling layer 524 and the lower coupling layer 314 can contain ruthenium.

[0042] Fig. Figure 6 shows a schematic representation of the MTJ stack 150 and illustrates the operating principle of the spin diode device 500. Fig. 5. The magnetization directions of the upper magnetic film 322 and the further upper magnetic film 326 can be antiparallel, and these upper magnetic films 322, 326 can have different natural FMR frequencies. For example, the natural FMR frequency of the upper magnetic film 322 f U1 be, while the natural FMR frequency of the further upper magnetic film 326 f U2 The spin diode device 100 can be configured to detect microwaves according to one of the frequencies f L1 f L2 f U1 or f U2oscillate. In other words, the Spin Diode Device 500 can detect microwaves of four different frequencies. When the incident microwaves have a frequency of f U1 If the incident microwaves have a frequency of f U2 According to the description, only the uppermost magnetic film 326 enters the FMR. Fig. 2. The effective resistance of the MTJ 150 changes when one of the magnetic films resonates, creating a rectifying effect in the spin diode device 500, which enables the spin diode device 500 to detect the microwave.

[0043] While spin diode devices 300 and 500 comprise two magnetic layers in each of the lower magnetic layer 102 and the upper magnetic layer 106, the lower magnetic layer 102 and the upper magnetic layer 106 can comprise more than two magnetic films. Each magnetic film can be separated from an underlying magnetic film by a coupling layer similar to the lower coupling layer 314 or the upper coupling layer 514, or by a separating layer similar to the separating layer 324. For example, the lower magnetic layer 102 can have another lower coupling layer over the further lower magnetic film 316, and a second further lower magnetic film over the further lower coupling layer.Similarly, the upper magnetic layer 106 can comprise a further upper coupling layer or a further separating layer above the further upper magnetic film 326 and a second further upper magnetic film above the further upper coupling layer or the further separating layer.

[0044] The spin diode devices 100, 300, and 500 described above offer several advantages compared to prior art devices. By using PMA in each of the lower and upper magnetic layers 102 and 106, both magnetic layers can detect microwaves with high sensitivity down to -50 dBm by operating in FMR mode. These magnetic layers can operate in FMR mode without requiring external bias energy to rotate the magnetization directions to the perpendicular directions. As such, the spin diode devices are always "ON" since it is not necessary to supply the devices with an external current or magnetic field. Furthermore, both the lower and upper magnetic layers 102 and 106 are capable of making microwaves of at least one frequency usable.In embodiments where the lower magnetic layer 102 and / or the upper magnetic layer 106 comprises more than one magnetic film separated by an exchange coupling layer between the layers, the spin diode device can be capable of simultaneously detecting or utilizing microwaves of three or more different frequencies. Each magnetic layer in the MTJ stack 150 can be structured to have a PMA thickness specific to the desired application. For example, M. eff 800 Oe for the use of 2.4 GHz microwaves and M eff 1650 Oe for the use of 5 GHz microwaves, where one Oe corresponds to approximately 79.5775 A / m. The spin diode device can be easily calibrated for sensor applications, as the FMR frequency is linearly related to the M effand is thus correlated with the PMA strength of the magnetic films. The spin diode device can also be smaller compared to conventional spin diode devices.

[0045] According to various non-restrictive embodiments, the spin diode devices 100, 300, 500 may be able to detect microwaves with frequencies in the range of about 1 GHz to about 100 GHz.

[0046] Fig. Figure 7 shows an electrical circuit diagram of a microwave device 700 according to various non-limiting embodiments. The microwave device 700 can comprise at least one spin diode 720. The spin diode 720 can be one of the spin diode devices 100, 300, or 500. The microwave device 700 can further comprise at least one antenna 702, at least one impedance matching network 704, a DC combiner 706, and a DC-DC converter 708. The at least one antenna 702 can be configured to receive microwaves 710. The received microwaves can pass through the impedance matching network 704 to reach the spin diode 720. Each set of an antenna 702, an impedance matching network, and a spin diode 720 can be connected in parallel with other similar sets.The DC combiner 706 can be configured to receive the outputs of each spin diode 720, and it can further be configured to combine their outputs to supply them to the DC-DC converter 708, which can be connected to a load 750.

[0047] Fig.Figure 8 shows an electrical circuit diagram of a microwave device 800 according to various, non-limiting embodiments. The microwave device 800 can be similar to the microwave device 700, but with a different connection of its components. In the microwave device 800, at least one antenna 702 can be connected to a radio frequency (RF) combiner 806. The RF combiner 806 can combine the microwave signals received by the at least one antenna 702 and provide a combined RF signal via the impedance matching network 704 to a group of spintronic devices 720. The output of the array of spintronic devices 720 can be provided to the DC-DC converter 708.

[0048] According to various non-limiting embodiments, the microwave device 700 or 800 can be configured to process input microwaves with a power of -10 dBm or less. Furthermore, the sensitivity of the microwave device 700 or 800 may depend on other factors, such as increased microwave loss due to additional impedance from extra lines / components.

[0049] Aspects of the present invention and certain features, advantages, and details thereof are explained in more detail below with reference to the non-limiting examples illustrated in the accompanying drawings. A description of known materials, manufacturing tools, processing techniques, etc., is omitted in order to avoid overburdening the invention with unnecessary detail. It is understood, however, that while the detailed description and specific examples illustrate aspects of the invention, they serve only for illustrative purposes and do not constitute a limitation. Various substitutions, modifications, additions, and / or arrangements within the nature and / or scope of the underlying inventive concepts are apparent to a person skilled in the art from this invention.

[0050] An imprecise language, such as that used in the description and claims, can be used to modify any quantitative representation that can permissibly change without altering the underlying function to which it refers. Accordingly, a value modified by one or more terms such as "approximately" or "about" is not restricted to the precisely stated value. In some cases, the imprecise language may correspond to the accuracy of a measuring instrument. Furthermore, a direction is modified by one or more terms such as "essentially" to clarify that the direction must be within the tolerances customary in the semiconductor industry.For example, “essentially parallel” means that they extend largely in the same direction within tolerances commonly used in the semiconductor industry, and “essentially perpendicular” means that they have an angle of ninety degrees plus or minus a tolerance commonly used in the semiconductor industry.

[0051] The term "connected" as used here refers to two physical elements and implies a direct connection between them. However, the term "coupled" can mean a direct connection or a connection via one or more intermediate elements.

[0052] Combinations such as "at least one of A, B or C", "one or more of A, B or C", "at least one of A, B and C", "one or more of A, B and C", and "A, B, C or any combination thereof" include any combination of A, B and / or C and may include multiples of A, multiples of B, or multiples of C. In particular, combinations such as "at least one of A, B or C", "one or more of A, B or C", "at least one of A, B and C", "one or more of A, B and C", and "A, B, C or any combination thereof" may be only A, only B, only C, A and B, A and C, B and C, or A and B and C, with each of these combinations being able to include one or more members of A, B, or C.

Claims

[1] Spin diode device (100; 300; 500) configured to detect a microwave signal oscillating at a first target oscillation frequency or a second target oscillation frequency, the spin diode device (100; 300; 500) comprising: a magnetic tunnel contact stack (150) arranged between a lower electrode (130) and an upper electrode (140), the magnetic tunnel contact stack (150) comprising: a lower magnetic layer (102) with a lower magnetic film (312); a tunnel barrier layer (104) above the lower magnetic layer (102), wherein the tunnel barrier layer (104) comprises an insulating material; and an upper magnetic layer (106) above the tunnel barrier layer (104), wherein the upper magnetic layer (106) comprises an upper magnetic film (322); wherein each of the lower magnetic film (312) and the upper magnetic film (322) has a perpendicular magnetic anisotropy, wherein the lower magnetic film (312) comprises a first strength of perpendicular magnetic anisotropy corresponding to a first natural ferromagnetic resonance frequency, wherein the first natural ferromagnetic resonance frequency corresponds to the first target oscillation frequency, wherein the upper magnetic film (322) comprises a second strength of perpendicular magnetic anisotropy corresponding to a second natural ferromagnetic resonance frequency, wherein the second natural ferromagnetic resonance frequency corresponds to the second target oscillation frequency, where the second strength of perpendicular magnetic anisotropy differs from the first strength of perpendicular magnetic anisotropy, and where the second natural ferromagnetic resonance frequency differs from the first natural ferromagnetic resonance frequency. [2] Spin diode device (100; 300; 500) according to claim 1, wherein the magnetization directions of the lower magnetic film (312) and the upper magnetic film (322) are antiparallel. [3] Spin diode device (100; 300; 500) according to claim 1, wherein each of the lower magnetic layer (102) and the upper magnetic layer (106) comprises a synthetic antiferromagnet. [4] Spin diode device (100; 300; 500) according to claim 3, wherein a resistance across the magnetic tunnel contact stack (150) changes when one of the lower magnetic film (312) and the upper magnetic film (322) absorbs the microwave oscillating at the first target oscillation frequency or the second target oscillation frequency, wherein the spin diode device (100; 300; 500) is configured to detect the microwave based on the change in resistance across the magnetic tunnel contact stack (150). [5] Spin diode device (300; 500) according to claim 1, wherein the lower magnetic layer (102) further comprises: a lower coupling layer (314) above the lower magnetic film (312), and a further lower magnetic film (316) above the lower coupling layer (314), wherein the further lower magnetic film (316) has a third strength of perpendicular magnetic anisotropy corresponding to a third natural ferromagnetic resonance frequency, wherein the third natural ferromagnetic resonance frequency corresponds to a third target oscillation frequency, such that the spin diode device (300; 500) is further configured to detect a microwave signal oscillating at the third target oscillation frequency, wherein the third strength of perpendicular magnetic anisotropy differs from each of the first strength of perpendicular magnetic anisotropy and the second strength of perpendicular magnetic anisotropy, and where the third natural ferromagnetic resonance frequency differs from each of the first natural ferromagnetic resonance frequencies and the second natural ferromagnetic resonance frequencies. [6] Spin diode device (300; 500) according to claim 5, wherein the magnetization directions of the lower magnetic film (312) and the further lower magnetic film (316) are antiparallel. [7] Spin diode device (300; 500) according to claim 5, wherein the lower coupling layer (314) is configured to provide an antiferromagnetic exchange between the lower magnetic film (312) and the further lower magnetic film (316). [8] Spin diode device (300; 500) according to claim 5, wherein each of the lower magnetic film (312) and the further lower magnetic film (316) comprises at least one two-layer film, wherein each two-layer film comprises a cobalt-containing layer and a platinum-containing layer. [9] Spin diode device (300; 500) according to claim 8, wherein the at least one two-layer film of the lower magnetic film (312) comprises six two-layer films, and wherein the at least one two-layer film of the further lower magnetic film (316) comprises four two-layer films. [10] Spin diode device (300; 500) according to claim 8, wherein the cobalt-comprising layer has a thickness of about 0.2 to about 0.5 nm and wherein the platinum-comprising layer has a thickness of about 0.2 to about 0.5 nm. [11] Spin diode device (500) according to claim 1, wherein the upper magnetic layer (106) further comprises: an upper coupling layer (524) above the upper magnetic film (322), and a further upper magnetic film (326) above the upper coupling layer (524), wherein the further upper magnetic film (326) has a perpendicular magnetic anisotropy. [12] Spin diode device (500) according to claim 11, wherein the magnetization directions of the upper magnetic film (322) and the further upper magnetic film (326) are antiparallel. [13] Spin diode device (500) according to claim 11, wherein the upper magnetic film (322) and the further upper magnetic film (326) have different natural ferromagnetic resonance frequencies. [14] Spin diode device (500) according to claim 11, wherein each of the upper magnetic film (322) and the further upper magnetic film (326) comprises cobalt, iron, boron or alloys thereof. [15] Spin diode device (500) according to claim 11, wherein the thickness of each of the upper magnetic film (322) and the further upper magnetic film (326) is in the range of about 0.4 nm to about 2.0 nm. [16] Spin diode device (500) according to claim 11, wherein the upper coupling layer (524) is configured to provide an antiferromagnetic exchange between the upper magnetic film (322) and the further upper magnetic film (326). [17] Spin diode device (500) according to claim 11, wherein the upper coupling layer (524) comprises ruthenium.

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