Spin diode devices

Abstract

The present disclosure relates to a spin diode device. According to various embodiments, a spin diode device may include a magnetic tunnel junction stack. The magnetic tunnel junction stack may include a lower magnetic layer, a tunnel barrier layer located above the lower magnetic layer, and an upper magnetic layer located above the tunnel barrier layer. The lower magnetic layer may include a lower magnetic film. The tunnel barrier layer may include an insulating material. The upper magnetic layer may include an upper magnetic film. Each of the lower magnetic film and the upper magnetic film may have perpendicular magnetic anisotropy.

Description

Technical Field

[0001] Various embodiments relate to spin diode devices including magnetic tunnel junctions. Background Art

[0002] There is an increasing demand for microwave detection devices capable of detecting low-power microwaves. Existing solutions, such as spin diodes, generally perform poorly at low-power microwave detection. To improve the low-power performance of spin diodes, external energy is typically required to induce resonance in the spin diode's magnetic tunnel junction stack. However, the need for an external energy source for the spin diode results in a larger device size and limited device durability. Furthermore, existing spin diodes can only utilize microwaves within a single frequency bandwidth. Therefore, multiple spin diodes are needed to utilize microwaves across multiple frequency bandwidths. Summary of the Invention

[0003] According to various embodiments, a spin diode device is provided. The spin diode device may include a magnetic tunnel junction stack. The magnetic tunnel junction stack may include a lower magnetic layer, a tunnel barrier layer located above the lower magnetic layer, and an upper magnetic layer located above the tunnel barrier layer. The lower magnetic layer may include a lower magnetic film. The tunnel barrier layer includes an insulating material. The upper magnetic layer may include an upper magnetic film. Each of the lower magnetic film and the upper magnetic film may have perpendicular magnetic anisotropy. BRIEF DESCRIPTION OF THE DRAWINGS

[0004] In the accompanying drawings, like reference numerals generally refer to the same parts throughout the different views. The drawings are not necessarily drawn to scale, but emphasis is generally placed upon illustrating the principles of the invention. In the following description, various embodiments are described with reference to the following drawings, in which:

[0005] Figure 1 Schematic diagrams of spin diode devices according to various non-limiting embodiments are shown.

[0006] Figure 2 shows a schematic diagram of the MTJ stack and shows Figure 1 The working principle of the spin diode device.

[0007] Figure 3 A schematic diagram of a spin diode device 300 is shown, according to various non-limiting embodiments.

[0008] Figure 4 shows a schematic diagram of the MTJ stack and shows Figure 3 The working principle of the spin diode device.

[0009] Figure 5 Schematic diagrams of spin diode devices according to various non-limiting embodiments are shown.

[0010] Figure 6 shows a schematic diagram of the MTJ stack and shows Figure 5 The working principle of the spin diode device.

[0011] Figure 7 Circuit diagrams of microwave devices according to various non-limiting embodiments are shown.

[0012] Figure 8 Circuit diagrams of microwave devices according to various non-limiting embodiments are shown. DETAILED DESCRIPTION

[0013] Embodiments generally relate to spin diode devices including magnetic tunnel junctions. The spin diode devices can be spintronic devices. Spin diode devices can be used in various applications, such as Wi-Fi energy harvesting, embedded object sensors, microwave imaging for medical or nondestructive testing, and microwave sensors for military applications.

[0014] Figure 1 Schematic diagram of a spin diode device 100 according to various non-limiting embodiments is shown. The spin diode device 100 may include a lower electrode 130 and an upper electrode 140. The spin diode device 100 may include a magnetic tunnel junction (MTJ) stack 150 disposed between the lower electrode 130 and the upper electrode 140. The MTJ stack 150 may include three general layers, namely, a lower magnetic layer 102, an upper magnetic layer 106, and a tunnel barrier layer 104 disposed between the lower magnetic layer 102 and the upper magnetic layer 106.

[0015] The lower magnetic layer 102 may be disposed above the lower electrode 130. The tunnel barrier layer 104 may be disposed above the lower magnetic layer 102. The upper magnetic layer 106 may be disposed above the tunnel barrier layer 104. The tunnel barrier layer 104 may separate the lower magnetic layer 102 from the upper magnetic layer 106. The tunnel barrier layer 104 may be non-magnetic and may magnetically decouple the lower magnetic layer 102 from the upper magnetic layer 106. The upper electrode 140 may be disposed above the upper magnetic layer 106. The lower magnetic layer 102 and the upper magnetic layer 106 may each include at least one magnetic film having perpendicular magnetic anisotropy (PMA).

[0016] The tunnel barrier layer 104 may include magnesium oxide. In alternative embodiments, the tunnel barrier layer 104 may include aluminum oxide or other materials suitable for magnetically decoupling the overlying layer from the underlying layer. According to various non-limiting embodiments, the thickness of the tunnel barrier layer 104 may be approximately 0.8 nm to approximately 2.0 nm. The tunnel barrier layer 104 may be sufficiently thin so that electrons can tunnel through the tunnel barrier layer 104 from the upper magnetic layer 106 to the lower magnetic layer 102 or vice versa.

[0017] According to various non-limiting embodiments, the lower electrode 130 and the upper electrode 140 may each include tantalum. The thickness of each of the lower electrode 130 and the upper electrode 140 may be approximately 5 nm.

[0018] According to various non-limiting embodiments, the lower magnetic layer 102 and the upper magnetic layer 106 may each include a magnetic film having a PMA. For example, the lower magnetic layer 102 may include a lower magnetic film ( Figure 1 For example, the upper magnetic layer 106 may similarly include an upper magnetic film ( Figure 1 ). The magnetization direction 152 of the lower magnetic layer 102 may be opposite (in other words, antiparallel) to the magnetization direction 156 of the upper magnetic layer 106 .

[0019] Figure 2 FIG. 1 shows a schematic diagram of an MTJ stack 150 and illustrates the operating principle of the spin diode device 100. The lower magnetic layer 102, or more specifically, the lower magnetic film in the lower magnetic layer 102, may be configured to have a natural ferromagnetic resonance (FMR) frequency f L The upper magnetic layer 106, or specifically the upper magnetic film in the upper magnetic layer 106, may be constructed to have an intrinsic FMR f U The intrinsic FMR frequency of a magnetic film is the frequency at which the precession motion of the magnetization in the magnetic film couples with the incident microwave radiation in the absence of an external magnetic field.

[0020] In the presence of oscillations to frequency f L When microwaves are applied to the lower magnetic layer 102, rather than the upper magnetic layer 106, the microwave energy can be absorbed. The absorbed microwave energy can excite the magnetic moment in the lower magnetic film in the lower magnetic layer 102 to FMR. As a result, the magnetization direction of the lower magnetic layer 102 can change from, for example, the perpendicular direction 152 to a new direction 112. The new direction 112 can include an in-plane component 114. The change in direction from the perpendicular direction 152 to the new direction 112 can be a slight shift such that the new direction 112 is closer to the perpendicular direction 152 than to the in-plane direction.

[0021] The magnetization direction of the upper magnetic layer 106 can remain relatively unchanged compared to the magnetization direction of the lower magnetic layer 102. A 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, thereby resulting in a rectifying effect across the MTJ stack 150. The change in the effective resistance across the MTJ stack 150 can change the magnitude and / or direction of the current flowing between the lower electrode 130 and the upper electrode 140. The spin diode device 100 can detect microwaves based on at least one of the magnitude of the current, the direction of the current, or a combination thereof.

[0022] On the other hand, if the microwave incident on the spin diode device 100 oscillates to a frequency f U , the upper magnetic layer 106 can absorb significantly more microwave energy than the lower magnetic layer 102. The absorbed microwave energy can excite electrons in the upper magnetic film in the upper magnetic layer 106 to FMR. As a result, the magnetization direction of the upper magnetic layer 106 can change from, for example, 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 the magnetization direction 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, thereby resulting in a rectifying effect across the MTJ stack 150. The change in the effective resistance across the MTJ stack 150 can change the magnitude and / or direction of the current flowing between the lower electrode 130 and the upper electrode 140. The spin diode device 100 can detect microwaves based on at least one of the magnitude of the current, the direction of the current, or a combination thereof.

[0023] Furthermore, the change in the effective resistance of the MTJ stack 150 caused by the change in the magnetization direction of the upper magnetic layer 106 may be different from the change in the effective resistance of the MTJ stack 150 caused by the change in the magnetization direction of the lower magnetic layer 102. Therefore, the spin diode device 100 may also determine the oscillation frequency of the microwaves based on the magnitude and direction of the current flowing between the lower electrode 130 and the upper electrode 140.

[0024] Although Figure 2 The lower magnetic layer 102 and the upper magnetic layer 106 are shown with opposite magnetization directions, ie, antiparallel, but in alternative embodiments, the lower magnetic layer 102 and the upper magnetic layer 106 may have the same magnetization direction.

[0025] Figure 3 A schematic diagram of a spin diode device 300 is shown, according to various non-limiting embodiments.

[0026] The lower magnetic layer 102 may include a lower magnetic film 312 . The lower magnetic layer 102 may further include a lower coupling layer 314 disposed over the lower magnetic film 312 , and another lower magnetic film 316 disposed over the lower coupling layer 314 .

[0027] The lower magnetic film 312 and the additional lower magnetic film 316 may each include cobalt, platinum, or combinations thereof. In alternative embodiments, the lower magnetic film 312 and the additional lower magnetic film 316 may include various combinations of nickel, terbium, palladium, iron, boron, or other metals or combinations thereof. The different elements in the lower magnetic film 312 and the additional lower magnetic film 316 may be formed from continuous layers or alloyed, so in some embodiments, the lower magnetic film 312 and the additional lower magnetic film 316 may independently include multiple sublayers. In embodiments where there are only two magnetic films in the lower magnetic layer 102, the magnetic properties of the combined lower magnetic film 312 and the additional lower magnetic film 316 may be the magnetic properties of the lower magnetic layer 102. The lower magnetic film 312 and the additional lower magnetic film 316 may include a pinned layer.

[0028] According to various non-limiting embodiments, each of the lower magnetic film 312 and the further lower magnetic film 316 can include at least one bilayer film, such as a film containing cobalt and another film containing platinum, such as a Co / Pt film, disposed above or below the film. The lower magnetic film 312 can include a plurality of bilayer films disposed in a stacked, continuous pattern. For example, the lower magnetic film 312 can include up to six such bilayer films, i.e., [Co / Pt]6. For example, the further lower magnetic film 316 can include up to four such bilayer films, i.e., [Co / Pt]4. The number of required bilayer film repetitions can depend on the target microwave frequency. Generally speaking, the higher the target microwave frequency, the more bilayer films are required.

[0029] Each of the lower magnetic films 312, 316 may be magnetically anisotropic and may have PMA. The FMR frequency f of the lower magnetic layer 102 L The thickness of the film including the cobalt-containing film and the other platinum-containing film may depend on the thickness of the film. For example, for an operating frequency range of about 20 GHz to about 60 GHz, the thickness of each of the cobalt film and the platinum film may be about 0.2 to 0.5 nm. In an exemplary embodiment, a two-layer film stack may include 0.4 nm of cobalt and 0.4 nm of platinum.

[0030] The lower coupling layer 314 may be an interlayer exchange coupling layer that provides antiferromagnetic exchange between the lower magnetic film 312 and the further lower magnetic film 316. The antiferromagnetic exchange can help reduce or compensate for stray magnetic field effects from the lower magnetic film 312 and the further lower magnetic film 316. The lower coupling layer 314 can force the magnetization directions of the lower magnetic film 312 and the further lower magnetic film 316 to be antiparallel. By having opposite magnetization directions, the lower magnetic film 312 and the further lower magnetic film 316 can resonate at different frequencies, thereby absorbing microwaves with different frequency bandwidths. The lower coupling layer 314 may include ruthenium (Ru), iridium (Ir), rhodium (Rh), or other materials. In various non-limiting embodiments, the lower coupling layer 314 may include approximately 50 to approximately 100 weight percent or approximately 80 to 100 weight percent ruthenium, based on the total weight of the lower coupling layer 314. The thickness of the lower coupling layer 314 may be approximately 0.3 nm to 0.9 nm.

[0031] The upper magnetic layer 106 may cover the tunnel barrier layer 104. The upper magnetic layer 106 may include an upper magnetic film 322. The upper magnetic layer 106 may also include an insertion layer 324 located above the upper magnetic film 322, and an additional upper magnetic film 326 located above the insertion layer 324. The upper magnetic film 322 and the additional upper magnetic film 326 may include pinned layers. For example, the upper magnetic film 322 may include at least one pinned layer, and the additional upper magnetic film 326 may also include at least one pinned layer. The upper magnetic films 322, 326 may have the same composition, or they may have different compositions, and there may be more, fewer, or the same number of pinned layers in the upper magnetic films 322, 326. The elements in the upper magnetic films 322, 326 may exist as an alloy or as a pure material layer or alloy layer. The upper magnetic films 322, 326 may include cobalt, iron, boron, alloys thereof, or mixtures thereof. For example, each of the upper magnetic films 322, 326 may include a cobalt-iron-boron alloy, such as Co 20 Fe 60 B 20 The upper magnetic films 322 and 326 may be magnetically "soft" so that their spin transfer torque and magnetization direction are variable. Each of the upper magnetic films 322 and 326 may be magnetically anisotropic and may have a PMA. The thickness of each of the upper magnetic films 322 and 326 may be approximately 0.3 nm to approximately 1.2 nm.

[0032] An insertion layer 324 may be disposed between the upper magnetic film 322 and the further upper magnetic film 326. The insertion layer 324 may be non-magnetic. The insertion layer 324 may provide ferromagnetic coupling between the upper magnetic films 322 and 326 and may be sufficiently thin to be amorphous. In alternative embodiments, the insertion layer 324 may be crystalline. The insertion layer 324 may include tantalum, molybdenum, tungsten, iron, or other compositions as alloys or as individual elements. According to various non-limiting embodiments, the thickness of the insertion layer 324 may be approximately 0.4 nm.

[0033] The thickness of the lower magnetic films 312, 316 and the upper magnetic films 322, 326 is critical for achieving PMA and may directly affect the natural FMR frequencies of these magnetic films. The natural FMR frequencies of these magnetic films may determine the operating frequency of the spin diode device 300. The spin diode device 300 can be configured to detect microwaves oscillating at a frequency that matches or coincides with the natural FMR frequencies of the lower magnetic films 312, 316. The spin diode device 300 can be configured to detect microwaves oscillating at a frequency that matches or coincides with the natural FMR frequencies of the upper magnetic films 322, 326.

[0034] Generally, the FMR frequency f of a magnetic film can be determined as follows:

[0035] f=γ(H ext +4πM eff )

[0036] Where γ represents the gyromagnetic coefficient of the magnetic film material, and H ext represents the external magnetic field strength, and where M eff Represents the effective PMA strength of the magnetic film. M eff Indicates the amount of external energy required to change the magnetization direction of a magnetic film from perpendicular to in-plane.

[0037] The spin diode device 100 can operate without the need for an external magnetic field, so H ext = 0. Therefore, the intrinsic FMR frequency of the magnetic film can be expressed as:

[0038] f=4πγM eff

[0039] In other words, the FMR frequency of each magnetic film can be determined by the MMR frequency which mainly depends on the interface effect and the bulk effect. effproportional. The interface effect may be caused by the orbital deformation caused by the breaking of the periodicity at the interface. The bulk effect may be caused by the orbital deformation caused by the asymmetry of the crystal space. At the interface of the magnetic film, the electrons may have additional magnetic energy due to the spin-orbit interaction. This additional energy may be so large that the equilibrium magnetization direction of the magnetic film becomes perpendicular to the plane, that is, located out of the plane. The PMA strength of the magnetic film may depend on the thickness of the magnetic film, its composition, crystallinity structure and the layers adjacent to the magnetic film.

[0040] For example, the thickness of the lower magnetic films 312 and 316 may be in the range of about 2 nm to about 10 nm to achieve a PMA having a natural FMR frequency, thereby achieving an operating frequency in the range of about 5 GHz to about 40 GHz. For example, the thickness of the upper magnetic films 322 and 326 may be in the range of about 1.5 nm to about 3.0 nm to achieve a PMA having a natural FMR frequency, thereby achieving 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 and 326 may be in the range of about 0.4 nm to about 2.0 nm to achieve a PMA having a natural FMR frequency, thereby achieving an operating frequency in the range of about 2 GHz to about 5 GHz.

[0041] The MTJ stack 150 may further include a seed layer 310. The seed layer 310 may cover the lower electrode 130. The seed layer 310 may be disposed below the lower magnetic layer 102 or below the lower magnetic film 312. The seed layer 310 may include platinum. In various embodiments, the seed layer 310 may also include nickel, chromium, ruthenium, tungsten, magnesium, holmium, or terbium. The seed layer 310 may have a thickness of approximately 5 nm. The thickness and material of the seed layer 310 are not necessarily limited to those described above, as long as the seed layer 310 can form a crystallization template for the lower magnetic film 312.

[0042] The MTJ stack 150 may also include a transition layer 318. The transition layer 318 may be disposed above the lower magnetic layer 102. The transition layer 318 may overlie the additional lower magnetic film 316 (if present in the lower magnetic layer 102). The transition layer 318 may be non-magnetic. In some embodiments, the transition layer 318 may include tantalum, iron, tungsten, molybdenum, terbium, iron, cobalt, or other elements as an alloy or as one or more pinning layers. The transition layer 318 may be used to disrupt the crystal structure of the underlying additional lower magnetic film 316 (or other pinning layers where more than two pinning layers are utilized). In some embodiments, the transition layer 318 may be amorphous. The transition layer 318 may be sufficiently thin that a crystalline structure may not form, for example, the thickness of the transition layer 318 may be approximately 0.2 nm to 0.5 nm. The transition layer 318 may be non-magnetic, and the amorphous nature of the transition layer 318 may allow for non-magnetic properties even in embodiments including iron, cobalt, or other materials that are generally magnetic.

[0043] The MTJ stack 150 may also include a polarizer layer 320. The polarizer layer 320 may overlie the transition layer 318. The polarizer layer 320 may be magnetic. In various embodiments, the polarizer layer 320 may include cobalt, iron, boron, alloys thereof, or combinations thereof, which may exist as alloys or as separate components and may exist as a single layer or multiple layers. In some embodiments, the polarizer layer 320 may have a crystal structure imparted to the overlying layer and may improve the spin polarization efficiency in the MTJ stack 150. The polarizer layer 320 may have a face-centered cubic crystal structure, but other types of crystal structures are also possible.

[0044] The MTJ stack 150 may further include a capping layer 330. The capping layer 330 may be disposed above the upper magnetic layer 106. The MTJ stack 150 may further include an optional top barrier layer 328 disposed above the upper magnetic layer 106. If the top barrier layer 328 is present, the capping layer 330 may cover the optional top barrier layer 328. Thus, in embodiments where the top barrier layer 328 is present, the upper magnetic layer 106 may be sandwiched between the tunnel barrier layer 104 and the top barrier layer 328. The upper electrode 140 may cover the capping layer 330. The capping layer 330 may further enhance the magnetic anisotropy effect of the MTJ stack 150. The capping layer 330 may include one or more of tungsten, magnesium oxide, ruthenium, platinum, hafnium, nickel-chromium, or other materials as alloys or elements. The capping layer 330 may be non-magnetic, and the composition of the capping layer 330 may depend on the materials of the upper magnetic films 322 and 326. In some embodiments, the optional top barrier layer 328 may include magnesium oxide and may be non-magnetic. The thickness of the cap layer 330 may be about 0.2 nm to about 2.0 nm. The thickness of the top barrier layer 328 may be about 1 nm.

[0045] According to various non-limiting embodiments, the spin diode device 300 can be manufactured using the same production line and process as the production of MRAM devices. The lower magnetic layer 102 can include a synthetic antiferromagnet (SAF), so that it can be a fixed layer. The upper magnetic layer 106 can be a free layer.

[0046] According to a non-limiting exemplary embodiment, the composition and thickness of each layer in the spin diode device 300 are described below. The thickness of each of the lower electrode 130 and the upper electrode 140 can be about 5 nm and can include tantalum. The thickness of the seed layer 310 can be about 5 nm and can include platinum. The lower magnetic film 312 can include six repeating bilayer films, the bilayer films including 0.4 nm of cobalt and 0.4 nm of platinum. The thickness of the lower coupling layer 314 can be about 0.4 nm and can include ruthenium. The additional lower magnetic film 316 can include four repeating bilayer films, the bilayer films including 0.4 nm of cobalt and 0.4 nm of platinum. The thickness of the transition layer 318 can be about 0.4 nm and can include tantalum. The thickness of the polarizer layer 320 can be about 1.0 nm and can include Co 20 Fe 60 B 20 The thickness of the tunnel barrier layer 104 may be about 1.0 nm and may include magnesium oxide. The thickness of the upper magnetic film 322 may be about 1.2 nm and may include Co 20 Fe 60 B 20 The thickness of the insertion layer 324 may be about 0.4 nm and may include tantalum. The thickness of the additional upper magnetic film 326 may be about 0.9 nm and may include Co 20 Fe 60 B 20 The top barrier layer 328 may be approximately 1.0 nm thick and may include magnesium oxide. The capping layer 330 may be approximately 1 nm thick and may include tungsten.

[0047] Figure 4 A schematic diagram of the MTJ stack 150 is shown, and Figure 3 The working principle of the spin diode device 300. Figure 3 In the illustrated embodiment, the lower magnetic layer 102 includes 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 may be antiparallel, and the lower magnetic films 312 and 316 may have different natural FMR frequencies. For example, the natural FMR frequency of the lower magnetic film 312 may be f L1 , and the natural FMR frequency of the lower magnetic film 316 may be f L2Due to the interlayer exchange coupling effect mediated by the thickness and material selection of the coupling layer 524, the magnetization directions of the upper magnetic film 322 and the additional upper magnetic film 326 can be the same. Therefore, the upper magnetic films 322 and 326 can act as a single intrinsic FMR frequency f U The spin diode device 300 may be configured to detect the L1 、f L2 or f U In other words, the spin diode device 300 can detect microwaves of three different frequencies. U When the frequency of the incident microwave is f L1 When the frequency of the incident microwave is f L2 When , only the other lower magnetic film 316 enters the FMR. Figure 2 As described, when any magnetic film resonates, the effective resistance of the MTJ 150 changes, thereby generating a rectifying effect in the spin diode device 300 , enabling the spin diode device 300 to detect microwaves.

[0048] Figure 5 A schematic diagram of a spin diode device 500 is shown, according to various non-limiting embodiments. Figure 5 The spin diode device 500 shown may be similar to Figure 3 The spin diode device 300 is shown, except that the insertion layer 324 is replaced by an upper coupling layer 524. The upper coupling layer 524 functions similarly to the lower coupling layer 314. The upper coupling layer 524 can also be an interlayer exchange coupling layer and can be used to maintain the antiparallel magnetization directions of the upper magnetic film 322 and the additional upper magnetic film 326. By having the antiparallel magnetization directions of the upper magnetic film 322 and the additional upper magnetic film 326, as well as the lower magnetic film 312 and the additional lower magnetic film 316, the spin diode device 100 can be configured to detect microwaves of four different frequencies. In the spin diode device 500, both the upper magnetic layer 102 and the lower magnetic layer 106 can include SAF. Each of the upper coupling layer 524 and the lower coupling layer 314 can include ruthenium.

[0049] Figure 6 A schematic diagram of the MTJ stack 150 is shown, and Figure 5 The working principle of the spin diode device 500 is shown in FIG. The magnetization directions of the upper magnetic film 322 and the additional upper magnetic film 326 may be antiparallel, and these upper magnetic films 322 and 326 may have different intrinsic FMR frequencies. For example, the intrinsic FMR frequency of the upper magnetic film 322 may be fU1 , and the natural FMR frequency of the upper magnetic film 326 may be f U2 The spin diode device 100 may be configured to detect the L1 、f L2 、f U1 or f U2 In other words, the spin diode device 500 can detect microwaves of four different frequencies. U1 When the frequency of the incident microwave is f U2 When , only the other upper magnetic film 326 enters the FMR. Figure 2 As described, when any magnetic film resonates, the effective resistance of the MTJ 150 changes, thereby generating a rectifying effect in the spin diode device 500 , enabling the spin diode device 500 to detect microwaves.

[0050] Although the spin diode devices 300 and 500 include two magnetic films in each of the lower magnetic layer 102 and the upper magnetic layer 106, it should be understood that the lower magnetic layer 102 and the upper magnetic layer 106 can include more than two magnetic films. Each magnetic film can be separated from the underlying magnetic film by a coupling layer similar to the lower coupling layer 314 or the upper coupling layer 514 or an insertion layer similar to the insertion layer 324. For example, the lower magnetic layer 102 can include an additional lower coupling layer located above the additional lower magnetic film 316, and a second additional lower magnetic film disposed above the additional lower coupling layer. Similarly, the upper magnetic layer 106 can include an additional upper coupling layer or an additional insertion layer located above the additional upper magnetic film 326, and a second additional upper magnetic film disposed above the additional upper coupling layer or the additional insertion layer.

[0051] The spin diode devices 100, 300, and 500 described above can achieve various advantages compared to devices in the prior art. By having PMA in each of the lower magnetic layer 102 and the upper magnetic layer 106, both magnetic layers can detect microwaves with a high sensitivity of up to -50 dBm by operating in FMR mode. These magnetic layers can operate in FMR mode without any external bias energy to change the magnetization direction to a perpendicular direction. As a result, the spin diode device is always in the "ON" state because no external current or magnetic field is required to power the device. In addition, each of the lower magnetic layer 102 and the upper magnetic layer 106 can utilize microwaves of at least one frequency. In embodiments where the lower magnetic layer 102 and / or the upper magnetic layer 106 include more than one magnetic film separated by an interlayer exchange coupling layer, the spin diode device can simultaneously detect or utilize microwaves of three or more different frequencies. Each magnetic film in the MTJ stack 150 can be constructed to have a PMA strength specific to the desired application. For example, an M film equivalent to 800 Oe can be used. eff Used to collect 2.4GHz microwaves, equivalent to 1650Oe of M eff Used to collect 5 GHz microwaves. For sensing applications, spin diode devices can be easily calibrated because the FMR frequency is related to the M eff The spin diode device can also be smaller in size than conventional spin diode devices.

[0052] According to various non-limiting embodiments, the spin diode device 100 , 300 , 500 is capable of detecting microwaves having a frequency in the range of about 1 GHz to about 100 GHz.

[0053] Figure 7 1 shows a circuit diagram of a microwave device 700 according to various non-limiting embodiments. The microwave device 700 may include at least one spin diode 720. The spin diode 720 may include any one of the spin diode devices 100, 300, or 500. The microwave device 700 may also include at least one antenna 702, at least one impedance matching network 704, a direct current (DC) combiner 706, and a DC-DC converter 708. The at least one antenna 702 may be configured to receive microwaves 710. The received microwaves may pass through the impedance matching network 704 and reach the spin diode 720. A group of antennas 702, impedance matching networks, and spin diodes 720 may be connected in parallel to other similar groups. The DC combiner 706 may be configured to receive the output of each spin diode 720 and may further be configured to combine their outputs to provide to a DC-DC converter 708, which may be connected to a load 750.

[0054] Figure 8A circuit diagram of a microwave device 800 according to various non-limiting embodiments is shown. Microwave device 800 may be similar to microwave device 700, but the connections of its components may differ. In microwave device 800, at least one antenna 702 may be connected to a radio frequency (RF) combiner 806. RF combiner 806 may combine microwave signals received at at least one antenna 702 and provide the combined RF signal to an array of spintronic devices 720 via an impedance matching network 704. The output from the array of spintronic devices 720 may be provided to a DC-DC converter 708.

[0055] According to various non-limiting embodiments, microwave device 700 or 800 can be configured to utilize input microwaves with a power of -10 dBm or less. The sensitivity of microwave device 700 or 800 may also depend on other factors, such as increased microwave loss due to additional impedance from additional wiring / components.

[0056] Various aspects of the present invention and certain features, advantages and details thereof are explained more fully below with reference to the non-limiting examples shown in the accompanying drawings. Descriptions of well-known materials, manufacturing tools, processing techniques, etc. are omitted so as not to unnecessarily obscure the present invention with details. However, it should be understood that the detailed description and specific examples, while indicating aspects of the present invention, are given by way of illustration only and not by way of limitation. Various substitutions, modifications, additions and / or arrangements within the spirit and / or scope of the basic inventive concept will be apparent to those skilled in the art from this disclosure.

[0057] As used throughout the specification and claims, approximating language may be used to modify any quantitative expression that is permissible to vary without resulting in a change in the basic function to which it is related. Thus, a value modified by one or more terms such as "approximately," "about," or the like is not limited to the precise value specified. In some cases, approximate language may correspond to the precision of the instrument used to measure the value. In addition, when a direction is modified by one or more terms such as "substantially," it means that the direction applies within the normal tolerances of the semiconductor industry. For example, "substantially parallel" means extending in approximately the same direction within the normal tolerances of the semiconductor industry, while "substantially perpendicular" means an angle of ninety degrees plus or minus the normal tolerances of the semiconductor industry.

[0058] The terms used herein are for the purpose of describing specific examples only and are not intended to limit the present invention. As used herein, the singular forms "a", "an" and "the" are also intended to include the plural forms, unless the context clearly indicates otherwise. It will also be understood that the terms "comprise" (and any form of including, such as "comprises" and "comprising"), "have" (and any form of having, such as "has" and "having"), "inclue" (and any form of including, such as "includes" and "including"), and "contain" (and any form of containing, such as "contains" and "containing") are open-ended linking verbs. Thus, a method or apparatus that "comprises," "has," "includes," or "contains" one or more steps or elements has these one or more steps or elements, but is not limited to having only these one or more steps or elements. Similarly, a method step or apparatus element that "comprises," "has," "includes," or "contains" one or more features has these one or more features, but is not limited to having only these one or more features. In addition, a device or structure configured in a certain manner is configured at least in this manner, but may also be configured in ways not listed.

[0059] As used herein, when used to refer to two physical elements, the term "connected" indicates a direct connection between the two physical elements. However, the term "coupled" can indicate a direct connection or a connection through one or more intermediate elements.

[0060] As used herein, the terms "may" and "may be" indicate: the possibility of occurring under a set of circumstances; possessing a specified quality, characteristic, or function; and / or qualifying a verb by expressing one or more of the ability, function, or possibility associated with another verb. Thus, the use of "may" and "may be" indicates that the modifier is clearly suitable, permitted, or appropriate for the specified ability, function, or use, while taking into account that in certain circumstances the modifier is sometimes not suitable, permitted, or appropriate. For example, in certain circumstances, an event or ability can be expected, while in other circumstances, it cannot occur—a distinction captured by the terms "may" and "may be."

[0061] 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 include any combination of A, B, and / or C, and may include multiples of A, multiples of B, or multiples of C. Specifically, phrases 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, B, and C, where any such combination may include one or more members of A, B, or C.

[0062] The present invention may be embodied in other specific forms without departing from the spirit or essential characteristics of the present invention. The foregoing embodiments are therefore to be considered in all respects as illustrative rather than restrictive of the invention described herein. The scope of the present invention is therefore indicated by the appended claims rather than by the foregoing description, and all changes that come within the meaning and range of equivalents of the claims are intended to be embraced therein.

Claims

1. A microwave detection device, comprising: A spin diode device configured to detect a microwave signal oscillating at one of a first target oscillation frequency and a second target oscillation frequency, the spin diode device comprising: A magnetic tunnel junction stack is provided between a lower electrode and an upper electrode of the spin diode device, wherein the magnetic tunnel junction stack comprises: a lower magnetic layer including a lower magnetic film; a tunnel barrier layer located above the lower magnetic layer, the tunnel barrier layer comprising an insulating material; and an upper magnetic layer located above the tunnel barrier layer, the upper magnetic layer comprising an upper magnetic film; wherein each of the lower magnetic film and the upper magnetic film has perpendicular magnetic anisotropy, wherein the lower magnetic film comprises a first perpendicular magnetic anisotropy strength corresponding to a first natural ferromagnetic resonance frequency, the first natural ferromagnetic resonance frequency corresponding to the first target oscillation frequency, wherein the upper magnetic film comprises a second perpendicular magnetic anisotropy strength corresponding to a second natural ferromagnetic resonance frequency, the second natural ferromagnetic resonance frequency corresponding to the second target oscillation frequency, wherein the second perpendicular magnetic anisotropy strength is different from the first perpendicular magnetic anisotropy strength, The second natural ferromagnetic resonance frequency is different from the first natural ferromagnetic resonance frequency. 2 . The microwave detection device according to claim 1 , wherein magnetization directions of the lower magnetic film and the upper magnetic film are antiparallel. 3 . The microwave detection device according to claim 1 , wherein each of the lower magnetic layer and the upper magnetic layer comprises a synthetic antiferromagnet.

4. The microwave detection device according to claim 3 , wherein when the frequency of the microwave signal matches the first natural ferromagnetic resonance frequency and the lower magnetic film absorbs energy of the microwave signal to enter a ferromagnetic resonance mode, the resistance across the magnetic tunnel junction stack changes to a first resistance, and When the frequency of the microwave signal matches the second natural ferromagnetic resonance frequency and the upper magnetic film absorbs energy of the microwave signal to enter a ferromagnetic resonance mode, the resistance across the magnetic tunnel junction stack changes to a second resistance, wherein the microwave detection device is configured to detect the microwave signal based on the change in the resistance across the magnetic tunnel junction stack.

5. The microwave detection device according to claim 1 , wherein the spin diode device is further configured to detect the microwave signal oscillating at a third target oscillation frequency. The lower magnetic layer further comprises: a lower coupling layer located above the lower magnetic film, and an additional lower magnetic film located above the lower coupling layer, wherein the additional lower magnetic film has a third perpendicular magnetic anisotropy strength corresponding to a third natural ferromagnetic resonance frequency, the third natural ferromagnetic resonance frequency corresponding to the third target oscillation frequency, wherein the third perpendicular magnetic anisotropy strength is different from the first perpendicular magnetic anisotropy strength and the second perpendicular magnetic anisotropy strength, wherein the third natural ferromagnetic resonance frequency is different from the first natural ferromagnetic resonance frequency and the second natural ferromagnetic resonance frequency, and wherein the third target oscillation frequency is different from the first target oscillation frequency and the second target oscillation frequency. 6 . The microwave detection device according to claim 5 , wherein magnetization directions of the lower magnetic film and the further lower magnetic film are antiparallel. 7 . The microwave detection device according to claim 5 , wherein the lower coupling layer is configured to provide antiferromagnetic exchange between the lower magnetic film and the further lower magnetic film. 8 . The microwave detection device according to claim 5 , wherein each of the lower magnetic film and the additional lower magnetic film comprises at least one bilayer film, each bilayer film comprising a cobalt-containing layer and a platinum-containing layer. 9 . The microwave detection device according to claim 8 , wherein the at least one bilayer film in the lower magnetic film includes six bilayer films, and wherein the at least one bilayer film in the other lower magnetic film includes four bilayer films. 10 . The microwave detection device according to claim 8 , wherein the thickness of the cobalt-containing layer is in the range of 0.2 to 0.5 nm, and wherein the thickness of the platinum-containing layer is in the range of 0.2 to 0.5 nm.

11. The microwave detection device according to claim 1 , wherein the upper magnetic layer further comprises: an upper coupling layer located above the upper magnetic film, and An additional upper magnetic film is located above the upper coupling layer, wherein the additional upper magnetic film has perpendicular magnetic anisotropy. 12 . The microwave detection device according to claim 11 , wherein magnetization directions of the upper magnetic film and the further upper magnetic film are antiparallel. 13 . The microwave detection device according to claim 11 , wherein the upper magnetic film and the further upper magnetic film have different natural ferromagnetic resonance frequencies. 14 . The microwave detection device according to claim 11 , wherein each of the upper magnetic film and the additional upper magnetic film comprises cobalt, iron, boron, or an alloy thereof. 15 . The microwave detection device according to claim 11 , wherein a thickness of each of the upper magnetic film and the further upper magnetic film is in a range of 0.4 nm to 2.0 nm. 16 . The microwave detection device according to claim 11 , wherein the upper coupling layer is configured to provide antiferromagnetic exchange between the upper magnetic film and the further upper magnetic film. The microwave detection device according to claim 11 , wherein the upper coupling layer comprises ruthenium.

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