19 results about "Exchange bias" patented technology

The application discloses a magnetoelectric heterojunction film and a preparation method thereof. The magnetoelectric heterojunction film comprises a strontium titanate base layer, a strontium ruthenate electrode layer, a bismuth ferrite ferroelectric material layer and a SmCo-based ferromagnetic material layer which are stacked in sequence. The magnetoelectric heterojunction film has the multi-ferroelectric layer room-temperature magnetoelectric coupling effect and the excellent magnetic performance of the ferromagnetic layer, and the magnetoelectric coupling effect of the heterojunction film can be enhanced through the strong exchange bias effect at the interface.

A method to calculate performance of a magnetic element including a reference bilayer including a ferromagnetic reference layer having a reference magnetization and an antiferromagnetic layer pining the reference magnetization by exchange-bias, the antiferromagnetic layer including a metallic polycrystalline material having a grain volume distribution; the method including: measuring an exchange-bias field (Hex) of the antiferromagnetic layer as a function of temperature; fitting a grain volume distribution function to the measured exchange-bias fields (Hex) to determine parameters characterizing the volume distribution function; calculating a variation in the direction of the reference magnetization as a function of a direction of an exposure magnetic field (H); and calculating the exchange bias field (Hex) for any value of the in-plane exposure field (H).

The application discloses a multi-state memory unit based on anti-ferromagnetic, and relates to the technical field of spintronic devices, and aims to solve the problems that multi-bit storage of a single device cannot be realized and data writing is difficult in the prior art.The application comprises a magnetic tunnel junction, a bottom electrode layer serving as a current writing line, the magnetic tunnel junction is used for storing data, and the bottom electrode layer is used for providing spin-orbit torque to write data; the magnetic tunnel junction at least comprises a fixed layer, a barrier layer and a free layer; the free layer is adjacent to an anti-ferromagnetic layer, and exchange bias is formed between the anti-ferromagnetic layer and the free layer; a current is applied on the corresponding bottom electrode to reverse the direction of the free layer and the exchange bias to a direction perpendicular to the current; and the free layer and the exchange bias are controlled to reverse the angle by applying the current in the current writing line at different angles, so that more intermediate states can be obtained in the whole magnetic resistance range. Not only can the application realize magnetic field-free writing of data, but also can realize extremely stable multi-bit storage.

A method for fabricating a magnetic material with tunable magnetic properties, comprising the reactive sputtering of a Mn3N2 seed layer onto a substrate, annealing at a first temperature, depositing a Mn layer onto the Mn3N2 seed layer, cooling to a second lower temperature, and applying a capping layer to complete the magnetic material. The resulting structure includes a Si substrate with one or more MnNx layer(s) with tunable nitrogen contents, and a capping layer, exhibiting adjustable magnetic properties such as exchange bias. A single Mn4N layer can be formed with this method, so can multilayers of Mn3N2 / Mn2N / Mn4N, or Mn2N / Mn4N, or other variations. Nitrogen partial pressure during deposition enables control of exchange bias by over an order of magnitude, while post-annealing reduces the bias by up to 70% through nitrogen migration into a neighboring tantalum layer. Voltage conditioning further tunes magnetic properties by driving nitrogen ions out of the Mn nitride layer, yielding an increased saturation magnetization and decreased exchange bias.

This invention discloses a two-dimensional van der Waals homogeneous structure with adjustable exchange bias, relating to the field of magnetic storage technology. The invention comprises a two-dimensional van der Waals ferromagnetic layer and a two-dimensional van der Waals antiferromagnetic layer stacked on top of each other. The thickness of both the ferromagnetic and antiferromagnetic layers is 2-200 nm, and the thickness ratio of the ferromagnetic and antiferromagnetic layers is x:(1-x), where x ranges from 0.1 to 0.9. The beneficial effect of this invention is that existing exchange bias methods are difficult to control in terms of bias magnitude. Even when an exchange bias can be induced, the magnitude of the exchange bias field cannot be controlled. This invention achieves and controls the exchange bias magnitude by adjusting the relative proportion of the thicknesses of the ferromagnetic and antiferromagnetic layers. The higher the proportion of the antiferromagnetic layer, the larger the exchange bias field.

The invention relates to the technical field of magnetic recording media and magnetic multifunctional materials, in particular to double perovskite oxide ceramic with an exchange bias effect and a preparation method of the double perovskite oxide ceramic. The chemical formula of the ceramic is Nd2-xSrxCoMnO6, the molar doping amount x of Sr < 2 + > is more than or equal to 0.0 and less than or equal to 0.5, and the ceramic has a single-phase orthogonal structure. The preparation method comprises the following steps: proportionally mixing the raw materials, and sintering in three stages to obtain the ceramic. When Sr < 2 + > is not doped, the oxygen vacancy defect causes a spin structure change and causes an exchange bias effect, under a 1kOe cooling magnetic field, the exchange bias field is 2.8 kOe, and the exchange bias does not have a magnetic exercise effect; when Sr < 2 + > is doped, the crystal structure and the spin structure change, the exchange bias field is 2.1-3.6 kOe, and the Curie temperature is 128-141K. The ceramic is stable in performance, the preparation process is simple and easy to control, and the ceramic is suitable for industrial production and suitable for the field of electronic components such as high-density magnetic storage.

The invention discloses a preparation method of a permanent magnet material with an exchange bias effect. The method comprises the following steps: weighing a Pr-Al-Cu alloy raw material, smelting, ball-milling, mixing with an organic solvent to prepare a diffusion source, uniformly coating the surface of a neodymium-iron-boron magnet with the diffusion source, and completing two-stage gradient diffusion heat treatment in a vacuum atmosphere. According to the neodymium-iron-boron magnet subjected to diffusion treatment, it is found through tests that a continuous and compact non-magnetic grain boundary phase is formed at the grain boundary of the diffused neodymium-iron-boron magnet, meanwhile, under the action of an external magnetic field, an antiferromagnetic grain boundary phase Pr6Fe13Cu generates a strong magnetic moment pinning effect on a main phase Nd2Fe14B, and then a reverse external magnetic field needed by ferromagnetic phase magnetic moment inversion is improved; therefore, an exchange bias phenomenon is generated, and the coercive force of the neodymium-iron-boron magnet is effectively improved. The method is well compatible with existing grain boundary diffusion process equipment, does not need additional transformation cost, is easy to implement industrially, is relatively low in cost, and can effectively improve the thermal stability of the magnet.

The application relates to a magnetic memory, comprising: an MTJ device, comprising a first electrode, an MTJ layer and an AFM layer, the MTJ layer being arranged between the first electrode and the AFM layer; a second electrode, arranged on a side of the AFM layer away from the MTJ layer; and a heater, arranged on a side of the second electrode away from the AFM layer, used for heating the AFM layer to demagnetize the AFM layer; wherein in a write mode, a write current flows from one end of the second electrode to the other end. The magnetic memory places the heater on the side of the second electrode away from the AFM layer to heat the AFM layer, which can effectively demagnetize the AFM layer completely; after demagnetization, the magnetization direction of the AFM layer is determined by the SOT effect generated by the write current passing through the bottom electrode, and then the exchange bias between the AFM layer and the free layer is flipped, so that the magnetic moment of the free layer is flipped. The demagnetization of the AFM layer adopts the heat generated by the separate heater, and does not need to demagnetize the AFM layer through the Joule effect of the increased write current, so that the write power consumption of the storage chip is effectively reduced.

The invention discloses a voltage regulation and control magnetic memory based on a two-dimensional ferromagnetic / multiferroic heterostructure and a preparation method, the device is composed of a substrate, a multiferroic thin film layer, a two-dimensional ferromagnetic thin film layer, an upper electrode and a lower electrode, an uncompensated magnetic moment is generated on an interface through ferroelectric polarization of the multiferroic layer, and the uncompensated magnetic moment and the two-dimensional ferromagnetic layer form exchange bias. And the ferroelectric polarization direction can be reversed by applying low voltage, so that the external magnetic field-free and nonvolatile regulation and control of the magnetization of the two-dimensional ferromagnetic layer are realized. The preparation method comprises the steps of magnetron sputtering growth of the multiferroic thin film, interface annealing treatment, molecular beam epitaxial growth of the two-dimensional ferromagnetic thin film and electrode preparation. The device has strong interface coupling, low power consumption, high regulation and control amplitude and good cycling stability at room temperature, wide-range voltage regulation and control of exchange bias can be realized, and a reliable technical scheme is provided for a novel low-power-consumption nonvolatile memory.

This invention relates to a magnetic tunnel junction memory cell based on magnetic skyrmions and its operation method. A magnetic tunnel junction memory cell may include: a reference magnetic layer and a free magnetic layer separated by a barrier layer; a skyrmion carrier layer separated from the free magnetic layer by a spacer layer, the spacer layer inducing ferromagnetic coupling or antiferromagnetic coupling between the skyrmion carrier layer and the free magnetic layer; and a cap layer formed on the skyrmion carrier layer, the cap layer applying a bias magnetic field to the skyrmion carrier layer by an exchange bias, such that the skyrmion carrier layer is in the skyrmion phase, wherein the cap layer generates a spin current when an in-plane write current is applied, the spin current being vertically injected into the skyrmion carrier layer to write skyrmions, and the skyrmions being coupled to the free magnetic layer through ferromagnetic coupling or antiferromagnetic coupling induced by the spacer layer.

The application belongs to the field of spin electronics and information technology, and provides a chiral / magnetic heterojunction device with exchange bias effect and a preparation method thereof, which comprises a substrate, a ferromagnetic material layer and a chiral material layer, and the ferromagnetic material layer and the chiral material layer are directly contacted and stacked and then placed above the substrate. Different chiral configurations of the chiral material layer correspond to different polarities of the exchange bias effect. The realization of the exchange bias effect is not limited by the types and preparation sequences of the ferromagnetic material layer and the chiral material layer, and through selection of chiral material layers with different configurations, the customized regulation and control of the polarity of the exchange bias effect can be realized, thereby providing a novel and feasible technical approach for realizing high-stability exchange bias effect.

The invention provides a preparation method of a Pr-Fe-B permanent magnet material with an exchange bias phenomenon, which comprises the following steps: weighing Pr, Fe, Cu and B according to the stoichiometric ratio of 70at% of Pr2Fe14B and 30at% of Pr6Fe13Cu, additionally adding 1wt% of Pr, carrying out electric arc melting, carrying out induction heating, spraying on a copper roller, crushing an obtained Pr2Fe14B-Pr6Fe13Cu alloy thin strip, and carrying out SPS sintering to obtain the Pr-Fe-B permanent magnet material. By adjusting the proportion of the alloy Pr2Fe14B to the alloy Pr6Fe13Cu, a continuous and thick non-magnetic grain boundary phase is formed in the grain boundary of the magnet, and the coercive force is greatly increased through decoupling intergranular exchange. And meanwhile, under the action of an external magnetic field, the antiferromagnetic phase Pr6Fe13Cu in the grain boundary generates a pinning effect on the main phase Pr2Fe14B, so that a larger reverse external magnetic field must be applied to realize complete overturning of the magnetic moment of the ferromagnetic phase, the exchange bias phenomenon is caused, and the coercive force of the magnet is improved. In addition, based on the advantages of low sintering temperature, short sintering time and the like of a discharge plasma rapid sintering technology, rapid growth of grains can be inhibited in the sintering process, so that grain refinement is realized.

A spin transfer torque (STT) magnetoresistive memory cell includes a magnetic tunnel junction including a reference layer, a free layer, and a nonmagnetic tunnel barrier located between the reference layer and the free layer, and perpendicular exchange bias layer in contact with the free layer.

This invention provides an orbital moment magnetic memory and its fabrication method. The orbital moment magnetic memory includes, from bottom to top, a substrate, an orbital Hall layer, a free layer, a barrier layer, and a fixing layer. The orbital Hall layer includes a metal layer and an FeMn layer arranged vertically. The free layer includes a first Co2Fe6B2 layer and an Fe3GaTe2 layer arranged vertically. The fixing layer includes a [Co / Pt] layer arranged vertically. n The structure consists of a first layer, a Ta layer, and a second Co2Fe6B2 layer. This structure utilizes the orbital Hall layer to efficiently generate orbital current, exchange bias field, and stray field, and leverages the strong spin-orbit coupling characteristics of the Fe3GaTe2 layer to achieve spin polarization and magnetization reversal at low current. This orbital-moment magnetic memory not only maintains a fast write speed while reducing power consumption, but also exhibits superior performance in high-speed data access, providing fundamental support for future applications in orbital electronics, magnetic storage, and other fields.

The application discloses a flexible thin film structure with a vertical exchange bias effect and a preparation method and application thereof, and belongs to the technical field of spin electronics and flexible integration. The flexible thin film structure with the vertical exchange bias effect comprises, from bottom to top, a polyimide flexible substrate, a wedge-shaped buffer layer, a wedge-shaped seed layer, a ferromagnetic layer, an anti-ferromagnetic layer and a protective layer; wherein the polyimide flexible substrate, the ferromagnetic layer, the anti-ferromagnetic layer and the protective layer are all flat structure layers. The thickness of the polyimide flexible substrate is set to 10-15 microns by simultaneously adopting the wedge-shaped buffer layer and the wedge-shaped seed layer between the polyimide flexible substrate and the magnetic layer, the film stress performance is improved by adopting the above structure, the CMOS (Complementary Metal-Oxide-Semiconductor) processing technology of a device can be completely compatible, the miniaturization and batch production of the flexible device can be realized, and the complexity of the preparation technology of the flexible electronic device in a wearable device is remarkably reduced.

The application provides a semi-metal compensation ferrimagnetic material, the chemical formula of the semi-metal compensation ferrimagnetic material is CrFeS2, the semi-metal compensation ferrimagnetic material has a hexagonal NiAs type crystal structure and belongs to the 194th space group, and a preparation method thereof comprises the following steps: sealing Cr powder, Fe powder and sulfur blocks and a transmission medium iodine in a vacuum quartz tube; placing the vacuum quartz tube in a heating furnace and heating at 780-920 DEG C for 4-30 days, and then quenching to a warm house. The semi-metal compensation ferrimagnetic material provided by the application has the characteristics of great perpendicular magnetic anisotropy and magnetic compensation characteristics, so that the material can realize zero-field cold exchange bias, and a unidirectional magnetic field with different sizes can control the direction of the exchange bias, and thus the material has a wide application prospect in the field of spintronics.

The invention provides a spin memory device based on antiferromagnetic exchange bias gradient and without magnetic field flipping and a preparation method thereof. The device comprises a plurality of minimum storage units, each unit comprises a substrate layer, a buffer layer and the like, a composite free layer comprises a ferromagnetic layer, a wedge-shaped exchange bias gradient control layer and the like, and the wedge-shaped layer regulates and controls the intensity gradient of an exchange bias field to realize non-magnetic field magnetization flipping. Preferably materials and parameters of each layer are given, and two write-in ends and one read-in end are arranged, so that read-write path independence and data read-write are realized. The preparation method comprises the steps of laminated deposition, graphical processing and top electrode integration. The composite free layer structure is innovatively designed, magnetic field auxiliary dependence is avoided, power consumption is reduced, and the working mode is expanded; the size of the storage unit can be reduced, the storage density is improved, the read-write energy consumption is reduced, and the reliability and service life of the device are improved.

The application relates to the field of magnetic storage, in particular to a magnetic storage unit structure. The application replaces the [ferromagnetic / non-magnetic layer]n multilayer coupling structure or the ferromagnetic layer / antiferromagnetic layer structure commonly used in the current SOT-MRAM core storage unit with the exchange bias interlayer structure ferromagnetic layer / ultra-thin metal interlayer / antiferromagnetic layer structure. Through the addition of the ultra-thin metal interlayer, the ferromagnetic and antiferromagnetic interface magnetic moments can be controlled by changing the interlayer metal material and its thickness, so that the coexistence of in-plane and out-of-plane exchange bias in the exchange bias structure is realized. Meanwhile, for storage, the out-of-plane exchange bias field is used to ensure the stability of the fixed layer of the storage unit, and the in-plane exchange bias field is used as the replacement of the required in-plane lateral field, so that the low-power consumption flipping of the information storage layer is realized without increasing the lateral magnetic field providing circuit, and the purpose of reducing the overall structure complexity is achieved.

The application discloses a kind of synergistically improves SrFeO 3‑δ Method of cubic perovskite structure spontaneous exchange bias effect relates to functional material preparation technical field.The method of the present application is by high-temperature solid-phase sintering,Er ions are doped in the Sr site of SrFeO 3‑δ Gradient magnetic Co ions are doped in the Fe site of SrFeO 3‑δ SrFeO 3‑δ Cubic perovskite structure with improved spontaneous exchange bias effect;The preparation process of the application is simple, the production cost is low, and the SrFeO 3‑δ Cubic perovskite structure prepared still can be offset along the magnetic field axis under zero magnetic field cooling condition, can realize stable unidirectional pinning effect without complex multilayer film structure or field cooling treatment, and is important to expand SrFeO 3‑δ Cubic perovskite oxide application field, improve device performance and promote the development of related scientific research.