28 results about "Antiferromagnetic coupling" patented technology

The invention provides a synthetic antiferromagnetic memory cell driven by spin orbit moment without magnetic field assistance, and belongs to the technical field of magnetic memory, the synthetic antiferromagnetic memory cell comprises a magnetic tunnel junction of a multilayer film structure, the magnetic tunnel junction comprises a heavy metal layer and a synthetic antiferromagnetic free layer located on the heavy metal layer; the tunneling insulating layer is located on the synthetic antiferromagnetic free layer, the reference layer is located on the tunneling insulating layer, and the metal electrode layer is located on the reference layer; wherein the synthetic antiferromagnetic free layer comprises an inclined vertical magnetic layer, a non-magnetic metal layer and a coupling magnetic layer which are stacked in sequence, and the inclined vertical magnetic layer and the coupling magnetic layer are subjected to antiferromagnetic coupling through the middle non-magnetic metal layer; the inclined perpendicular magnetic layer has inclined perpendicular anisotropy. According to the invention, deterministic magnetization flipping driven by spin orbit moment and resistance state control of the magnetic tunnel junction memory cell without the assistance of an external magnetic field are realized.

A magnetic memory device may include a magnetic track that extends in a first direction. The magnetic track may include a lower magnetic layer that extends in the first direction, an upper magnetic layer that extends in the first direction on the lower magnetic layer, a spacer layer that extends in the first direction between the lower magnetic layer and the upper magnetic layer, and a non-magnetic pattern that penetrates the upper magnetic layer and is on the spacer layer. The non-magnetic pattern has a first junction surface that is in contact with a first portion of the upper magnetic layer, and a second junction surface that is in contact with a second portion of the upper magnetic layer. The lower magnetic layer and the upper magnetic layer are antiferromagnetically coupled to each other by the spacer layer.

The invention discloses a three-dimensional magnetic sensor based on an abnormal Hall effect, and belongs to the technical field of spin electron sensors. The three-dimensional magnetic sensor comprises a substrate, an AHE thin film material layer with PMA, a rare earth material layer, a protective layer and a metal electrode layer which are sequentially arranged from bottom to top, the AHE thin film material layer with PMA is of a Pt / Co / Pt multi-layer thin film heterostructure, and the rare earth material layer is Dy. According to the three-dimensional magnetic sensor based on the abnormal Hall effect provided by the invention, a rare earth material Dy layer with a proper thickness grows on a Pt / Co / Pt structure, Co and Dy form antiferromagnetic coupling based on RKKY interaction, residual magnetism adjustment driving current and power consumption are reduced, so that magnetic hysteresis is reduced, and the driving current and power consumption are correspondingly reduced; and the existence of RKKY interaction does not change the multilayer film PMA, so that the linear range is kept unchanged.

The application provides a magnetic tunnel junction free layer and a magnetic tunnel junction structure with the same. The magnetic tunnel junction free layer comprises a first magnetic composite layer, an antiferromagnetic spacer structure and a second magnetic composite layer which are sequentially stacked along a first direction. The first magnetic composite layer and the second magnetic composite layer are in antiferromagnetic coupling under the action of the antiferromagnetic spacer structure, and the magnetization directions thereof are opposite. Since the above structure adopts a plurality of magnetic composite layers, the overall thickness of the magnetic layer is increased while the magnetization direction is controlled to be perpendicular to the film interface, thereby increasing the data retention capability of the device. In addition, in order to reduce the write current, the above structure makes the magnetization directions of different magnetic composite layers opposite, reduces the total magnetic moment of the overall structure, thereby reducing the write current and realizing high device erasing resistance. In addition, the structure can obtain a higher TMR, thereby improving the data reading speed.

This invention discloses a SOT-MRAM device, belonging to the field of magnetic random access memory technology. The SOT-MRAM device includes, from bottom to top, a bottom electrode, a spin orbital layer, a magnetic tunnel junction, an antiferromagnetic coupling layer, and a top electrode. The current propagation direction in the spin orbital layer is the same as its own long axis direction. The magnetic moment of the magnetic tunnel junction is perpendicular to its own film surface direction. The magnetic tunnel junction includes a free layer with bulk vertical anisotropy. An inclined sidewall is formed on one side of the free layer using an etching process, creating a continuous thickness gradient along the short axis of the spin orbital layer. This invention introduces structural asymmetry through the thickness gradient of the free layer, breaking the symmetry and replacing the effect of the traditional external magnetic field to achieve zero-magnetic-field flipping.

The application provides a magnetic tunnel junction device, comprising: a reference layer, a barrier layer, a free layer and a cap layer which are sequentially stacked, the reference layer has a fixed magnetization which is substantially perpendicular to the plane of the reference layer, the free layer comprises: a first ferromagnetic layer, a second ferromagnetic layer and an antiferromagnetic coupling layer between the first ferromagnetic layer and the second ferromagnetic layer, the first ferromagnetic layer is adjacent to the barrier layer, the first ferromagnetic layer has a magnetization which is perpendicular to the film surface and can be reversed, and the second ferromagnetic layer has a magnetization which is opposite to the magnetization direction of the first ferromagnetic layer. And a spacer layer is arranged between the two ferromagnetic layers of the free layer and the antiferromagnetic coupling layer or between the two ferromagnetic layers, so as to improve the saturation magnetization of the free layer. The magnetic tunnel junction device of the application has high perpendicular anisotropy and low switching current.

This application discloses a magnetic tunnel junction memory device based on a bismuth selenide and nickel iodide heterojunction substrate. The memory includes, from top to bottom, a top electrode, a SOT-MTJ, and a substrate. The SOT-MTJ includes, from top to bottom, a reference layer, a tunneling layer, a heavy metal layer, and a free layer. The substrate is a Bi2Se3 and NiI2 heterojunction structure. Bi2Se3 facilitates the conversion of current into spin-orbit torque, enabling current-induced field-free magnetization reversal. NiI2 has vertical magnetic anisotropy, which can reduce the critical reversal current. An artificial antiferromagnetic structure (CoFeB / MgO / Ta / W / CoFeB) with vertical magnetic anisotropy is adopted, with Ta / W composite heavy metal as the coupling layer. The two antiferromagnetically coupled CoFeB layers switch between parallel and antiparallel states under the action of SOT. Both Ta and W have large spin Hall angles, which are very beneficial for generating spin-orbit torque to reverse the magnetic moment.

The application discloses a magnetic multilayer film structure, comprising: a first multilayer structure formed on a buffer layer or a seed layer; the first multilayer structure comprises, in sequence: a reference layer, a non-magnetic intermediate layer, a free layer and a coupling layer; wherein the coupling layer and the free layer are antiferromagnetically or ferromagnetically coupled through an interface, the magnetic moment directions of the coupling layer and the free layer are antiparallel or parallel arranged, and the non-magnetic intermediate layer is used for isolation or insulation. The application utilizes the antiferromagnetic or ferromagnetic coupling of the coupling layer and the free layer through the interface, or the antiferromagnetic or ferromagnetic coupling of the coupling layer and the reference layer through the interface, the coupling effect of the interface provides strong perpendicular magnetic anisotropy, the thickness of the free layer or the reference layer can be further increased under the condition of guaranteeing the perpendicular magnetic anisotropy, thereby the TMR value is increased and the damping factor is reduced. When the coupling layer and the free layer are antiferromagnetically coupled, the magnetic moment directions form antiparallel arrangement, thereby the total saturation magnetization is reduced, and further the interference of an external magnetic field is reduced.

A magnetic memory device includes a magnetic track extending in a first direction. The magnetic track includes a lower magnetic layer, an upper magnetic layer on the lower magnetic layer, a non-magnetic pattern on the lower magnetic layer and at a side of the upper magnetic layer, and a spacer layer between the lower magnetic layer and the upper magnetic layer and extending between the lower magnetic layer and the non-magnetic pattern. The lower magnetic layer and the upper magnetic layer are antiferromagnetically coupled to each other by the spacer layer. The non-magnetic pattern has a first surface and a second surface which are opposite to each other in a second direction perpendicular to the first direction. A junction surface between the non-magnetic pattern and the upper magnetic layer is inclined with respect to a reference surface perpendicular to the first surface and the second surface.

The present invention relates to artificial antiferromagnetic multilayer film structures and magnetic random access memories including the same. According to an embodiment, an artificial antiferromagnetic multilayer film structure can include: an in-plane field coupling layer including a first ferromagnetic layer and a second ferromagnetic layer formed of a ferromagnetic conductive material, and a first spacer layer located between the first and second ferromagnetic layers, the first spacer layer being formed of a non-magnetic conductive material and inducing antiferromagnetic coupling between the first and second ferromagnetic layers; a free magnetic layer including a third ferromagnetic layer and a fourth ferromagnetic layer formed of a ferromagnetic conductive material, and a spin Hall effect layer located between the third and fourth ferromagnetic layers, the spin Hall effect layer being formed of a material having a spin Hall effect and inducing antiferromagnetic coupling between the third and fourth ferromagnetic layers; and an intermediate layer located between the in-plane field coupling layer and the free magnetic layer, the intermediate layer being formed of a non-magnetic material.

Provided is a magnetic skyrmion memory, comprising: a magnetic structural racetrack, a magnetic tunnel junction and a ferroelectric back gate. The magnetic structure racetrack comprises a topological material layer and a ferrimagnetic layer, and is constructed to comprises a middle region and extension parts respectively extending from both sides of the middle region; the ferrimagnetic layer of the extension parts on the both sides are respectively pinned by means of antiferromagnetic coupling in opposite magnetic moment directions; the magnetic tunnel junction is located above the middle region of the magnetic structure racetrack, and is configured to electrically read a resistance state change of the memory; the ferroelectric back gate comprises a ferroelectric layer and a bottom electrode, and is located below the middle region of the magnetic structure racetrack; when a current is injected into the topological material layer, a spin orbit moment is generated, so as to control the motion of the magnetic structure of the ferrimagnetic layer in the ferrimagnetic layer; a gate voltage is applied to adjust the polarization direction of the ferroelectric layer, so as to control the magnitude of an antisymmetric exchange interaction at an interface between the topological material layer and the ferrimagnetic layer, thereby finally enabling the memory to operate in a skyrmion mode or in a binary mode.

The invention discloses a current regulation and control low-pass filter based on a magnetic domain wall, which relates to the technical field of nano low-pass filters, and comprises a substrate, a buffer layer, a magnetic functional layer, an electrode assembly, a magnetoresistance detection module, a protective layer and a packaging structure, the magnetic domain wall adopts two antiferromagnetic coupling sub-layer structures, the electrode assembly comprises a signal input end and a signal output end, the signal input end and the signal output end are connected with the ferrocobalt electrodes, the ferrocobalt electrodes are connected to the two ends of the magnetic functional layer respectively, the magnetoresistance detection module is connected to the signal output end, and the magnetoresistance detection module is connected to the signal output end. And the magnetoresistance detection module is used for reading the filtered signal response. According to the current regulation and control low-pass filter based on the magnetic domain wall, the magnetoresistance technology is combined to serve as an output detection system, and efficient and low-power-consumption signal filtering is achieved through the magnetic domain wall dynamic characteristics and the magnetoresistance effect.

The present application relates to the technical field of microwave regulation, and particularly relates to a single-molecule quantum bit device based on microwave resonance regulation and a preparation method thereof.The quantum bit device takes a phenyl bridged copper-iron bis-porphyrin molecule or a phenyl bridged copper phthalocyanine-iron porphyrin molecule as a quantum bit functional molecule, and coordination metal ions in a main chain and a side chain of the molecule form a correlated ground state through anti-ferromagnetic coupling, the main chain metal ions play a function of stabilizing a spin environment, and the side chain metal ions serve as precise control sites, in a process of microwave-induced spin resonance, two spins are synchronously flipped to realize switching between 0 and 1; meanwhile, an entangled ground state formed by the main chain and the side chain can effectively block a tunneling electron inelastic scattering channel, inhibit spin flipping, and prolong spin lifetime, so as to maintain stability of a coherent state; the preparation method provided by the present application is simple to operate, reaction conditions are easy to control, and is helpful to scale production.

The application discloses a spin orbit torque magnetic memory based on a voltage-controlled magnetic anisotropy effect, which comprises an electrode layer and an SOT-MTJ (spin orbit torque magnetic tunnel junction) from top to bottom, wherein the SOT-MTJ comprises an artificial antiferromagnetic coupling layer, a reference layer, a tunneling layer, a free layer and an antiferromagnetic layer which are sequentially stacked from top to bottom. In the SOT-MTJ, an angle is formed between the long axis direction of the elliptical upper layer and the X axis direction of the bottom layer to generate a channel of an effect field Heff, and an auxiliary magnetic moment is more easily flipped. The bottom antiferromagnetic layer is made of IrMn or PtMn material, has a relatively large spin Hall angle, is beneficial to efficiently generating a spin orbit torque to flip a magnetic moment, and meanwhile, the IrMn and PtMn antiferromagnetic material can provide an exchange coupling field to replace an external field required by a coherent magnetic switch. In addition, a voltage is applied to the top and bottom of the magnetic memory, a very short voltage pulse is applied, an energy barrier during magnetization switching is reduced or even eliminated, and the free layer is induced to realize SOT deterministic switching faster.

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 invention relates to a vertical magneto-sensitive TMR sensor with a continuously adjustable linear region, belongs to the technical field of magnetic sensors, and solves the problems that a vertical magnetic field is difficult to measure and the linear region of the same sensor cannot be regulated and controlled in the prior art. The sensor comprises a Si substrate, a piezoelectric film layer, an electrode layer, a seed layer, a vertical magnetic free layer, a tunneling barrier layer, a vertical magnetic fixed layer and a protective layer from bottom to top, and the vertical magnetic free layer sequentially comprises a first magnetic material layer, a first ultrathin metal layer and a second magnetic material layer from bottom to top. And the vertical magnetic fixed layer comprises a ferromagnetic layer, a second ultrathin metal layer and an antiferromagnetic coupling layer from bottom to top. According to the sensor, the vertical magnetic anisotropy of the vertical magnetic free layer of the vertical magneto-sensitive TMR sensor is regulated and controlled by utilizing the stress generated by the piezoelectric material, continuous regulation and control in a linear range can be realized, the application scene of the sensor is remarkably expanded, and the preparation process is good in compatibility, convenient to package, low in cost and suitable for large-scale mass production.

The present disclosure generally relates to a dual free layer two dimensional magnetic recording read head. The read head comprises a first lower shield, a first sensor disposed over the first lower shield, a first upper shield disposed over the first sensor, a read separation gap (RSG) disposed on the first upper shield, a second lower shield disposed over the RSG, a second sensor disposed over the second lower shield, and a second upper shield disposed over the second sensor. In some embodiments, the second lower shield comprises a CoFeHf layer. In another embodiment, the second lower shield is a synthetic antiferromagnetic multilayer comprising a first shield layer, a second shield layer, and a CoFe / Ru / CoFe anti-ferromagnetic coupling layer or a Ru layer disposed therebetween, the first and second shield layers comprising NiFe and CoFe. In yet another embodiment, the second lower shield comprises layers of Ru, IrMn, and NiFe.

The present invention discloses a novel high-density FinFET memory and a method for fabricating the same. The memory comprises multiple memory cells on a substrate layer, each of which includes a current writing layer and two magnetic tunnel junctions of identical structure. The magnetic tunnel junctions comprise a free layer, a barrier layer, an artificial antiferromagnetic coupling layer, and a capping layer arranged in sequence, and the two magnetic tunnel junctions are located on either side of the current writing layer to form a symmetrical structure. The artificial antiferromagnetic coupling layer comprises a fixed layer, an antiferromagnetic coupling layer, and a pinning layer. The memory fabricated by the present invention utilizes two symmetrical magnetic tunnel junctions with opposite spin Hall angles to achieve differential storage. Multiple junction memory cells can be formed on a single current writing layer, thereby improving storage density. The differential structure of the memory cells reduces the use of source lines, word lines, and bit lines, thereby improving integration. The fabrication method of the present invention requires only a single deposition and etching process, making the method simple and easy to implement.

The application provides a true random number generator and a method for generating a true random number. The random number generation module of the true random number generator comprises a spin current generation layer and two magnetic tunnel junctions arranged side by side on the spin current generation layer. The spin current generation layer is provided with a first electrode and a second electrode for passing a first current at both ends. The two magnetic tunnel junctions each comprise a free layer, an insulating layer, a reference layer, a pinned layer and a cap layer stacked in sequence. The free layers of the two magnetic tunnel junctions are configured to have opposite magnetization directions after magnetic field initialization. The spacing between the two magnetic tunnel junctions is configured to enable the free layers to produce antiferromagnetic coupling. The cap layer and the first electrode of one of the two magnetic tunnel junctions are used to pass a second current. The application reduces the influence of stray magnetic fields on randomness by designing the antiferromagnetic coupling of the free layer, and can effectively improve the randomness of the true random number generator based on the spin-orbit torque effect.

The present disclosure generally relates to a two dimensional magnetic recording (TDMR) read head. The read head comprises a lower shield, a lower sensor disposed on the lower shield, a middle shield disposed over the lower sensor, an upper sensor disposed on the middle shield, and an upper shield disposed over the upper sensor. In one embodiment, the middle shield is a simple pinned shield comprising a first ferromagnetic (FM) layer, an antiferromagnetic (AFM) layer disposed on the first FM layer, and a second FM layer disposed on the AFM layer, and the upper shield is a synthetic antiferromagnetic (SAF) pinned shield comprising a first pinning layer, an antiferromagnetic coupling (AFC) layer disposed on the first pinning layer, and a second pinning layer disposed on the AFC layer. In another embodiment, the middle shield is a SAF pinned shield and the upper shield is a simple pinned shield.

Provided are a magnetic film, a magnetoresistance effect element and a magnetic memory which take advantages of atop-pinned structure and a bottom-pinned structure, maintain perpendicular magnetic anisotropy of magnetic layers in a fixing layer and allow strong pinning even in an annealing treatment after a protective film is formed.A fixing layer of a magnetic film has a basic configuration in which a first magnetic layer (21), a first non-magnetic layer (31), a first Pt layer (41), a second magnetic layer (22) disposed adjacent to each other in this order.The magnetization directions of the first magnetic layer (21) and the second magnetic layer (22) are both a direction perpendicular to the film surface, and an antiferromagnetic coupling is formed between the first magnetic layer (21) and the second magnetic layer (22).

The invention relates to the technical field of microwave regulation and control, in particular to a single-molecule quantum bit device based on microwave resonance regulation and control and a preparation method of the single-molecule quantum bit device. According to the quantum bit device, phenyl-bridged copper-iron bi-porphyrin molecules or phenyl-bridged copper phthalocyanine-iron porphyrin molecules are used as quantum bit functional molecules, coordination metal ions in a molecular main chain and a side chain form an associated ground state through antiferromagnetic coupling, and the main chain metal ions play a role in stabilizing a spinning environment; side chain metal ions are used as accurate control sites, and in the process of microwave-induced spin resonance, two spins are turned over synchronously to realize switching between 0 and 1; meanwhile, an entangled ground state formed by main-side chain coupling can effectively block a tunneling electron inelastic scattering channel, inhibit spin overturning and prolong the spin service life, so that the stability of a coherent state is maintained; the preparation method provided by the invention is simple and convenient to operate, reaction conditions are easy to control, and large-scale production is facilitated.

Provided is a magnetic skyrmion memory, comprising a magnetic structure raceway, a magnetic tunnel junction, and a ferroelectric back gate. The magnetic structure raceway comprises a topological material layer and a ferrimagnetic layer, and is configured to comprise a middle region and two extension parts respectively extending from two sides of the middle region, and the ferrimagnetic layers of the two extension parts are respectively anti-ferromagnetically coupled and pinned in opposite magnetic moment directions. The magnetic tunnel junction is located on the middle region of the magnetic structure raceway and is configured to be used for electrically reading memory resistance state changes. The ferroelectric back gate comprises a ferroelectric layer and a bottom electrode, and is located below the middle region of the magnetic structure raceway. When the topological material layer is injected with current, a spin-orbit torque is generated to regulate the movement of the magnetic structure in the ferrimagnetic layer. By applying a gate voltage to adjust the polarization direction of the ferroelectric layer, the size of the anti-symmetry exchange interaction at the interface between the topological material layer and the ferrimagnetic layer is regulated, and finally the memory is operated in a skyrmion mode or a binary mode.

This invention discloses a regenerated cathode material with orientation site-induced antiferromagnetic coupling, its preparation method, and its application. The regenerated cathode material with orientation site-induced antiferromagnetic coupling is a regenerated lithium nickel cobalt manganese oxide cathode material. The crystal structure of the regenerated lithium nickel cobalt manganese oxide cathode material contains niobium atoms, which occupy lithium sites in the crystal lattice and locally form Nb-O-Ni coordination structures. The preparation method is as follows: pre-treating waste lithium nickel cobalt manganese oxide cathode material to obtain a cathode material intermediate; mixing the cathode material intermediate, a lithium source, and a niobium source to obtain a powder to be sintered; subjecting the powder to be sintered to high-temperature calcination, and cooling to obtain the regenerated cathode material with orientation site-induced antiferromagnetic coupling. When applied to lithium-ion batteries, it exhibits long-term cycle stability.

This invention discloses a magnetic storage unit and a magnetic memory. The magnetic storage unit includes an upper electrode, a pinning layer, a coupling layer, a fixed magnetic layer, a tunneling barrier layer, a free magnetic layer, and a lower electrode. These components are stacked sequentially. The coupling layer enables antiferromagnetic coupling between the fixed magnetic layer and the pinning layer. The pinning layer eliminates stray fields from the fixed magnetic layer to the free magnetic layer, and a material-doped region is provided within the pinning layer. By providing the pinning layer, the stray field from the fixed magnetic layer to the free magnetic layer can be eliminated. The material-doped region within the pinning layer ensures that the stray field experienced by the free magnetic layer remains very small under temperature changes.

The present disclosure addresses the problem of providing a magnetic sensor capable of detecting a magnetic field while suppressing an increase in cost. A TMR film (10) of this magnetic sensor comprises a first magnetic layer (101) to a third magnetic layer (103), an insulating layer (104) sandwiched between the first magnetic layer (101) and the second magnetic layer (102), and a non-magnetic layer (105) sandwiched between the second magnetic layer (102) and the third magnetic layer (103). The second magnetic layer (102) and the third magnetic layer (103) are antiferromagnetically coupled via the nonmagnetic layer (105). The magnetization strength of the first magnetic layer (101) is equal to the magnetization strength of the third magnetic layer (103). The magnetization strength of the second magnetic layer (102) is less than the magnetization strength of the third magnetic layer (103). The strength of the antiferromagnetic coupling between the second magnetic layer (102) and the third magnetic layer (103) is greater than both the magnetization strength of the first magnetic layer (101) and the magnetization strength of the third magnetic layer (103).

The invention relates to the technical field of synthetic antiferromagnet domain wall oscillation dynamics, and discloses a synthetic antiferromagnet domain wall oscillation simulation system which comprises a synthetic antiferromagnet, a coupling analysis module and an oscillation simulation module. A coupling analysis module of the system adopts a rectangular coordinate system and a spherical coordinate system to jointly describe the domain wall of the synthetic antiferromagnet, the domain wall of an upper magnetic layer shows the spatial gradual change characteristic from bottom to top, the domain wall of a lower magnetic layer shows the spatial gradual change characteristic from top to bottom, and when the magnetization intensity vector polar angle of the magnetic layers is calculated, the domain wall of the synthetic antiferromagnet is calculated. A corresponding coupling differential equation is set for each magnetic layer, the magnetization dynamic process under the combined action of current, a magnetic field and interlayer antiferromagnetic coupling is accurately described, the unique mechanism of domain wall oscillation of the synthetic antiferromagnetic is revealed, the layered simulation precision is high, and the method is easy to implement. The oscillation simulation module calculates the total energy density, the energy surface density, the domain wall oscillation speed and the azimuth angle to form a synthetic antiferromagnet one-dimensional domain wall model, and the coupling analysis efficiency is high.

A magnetic tunnel junction device includes a pinned magnetic layer, a free magnetic layer, and a tunnel barrier layer between the pinned and free magnetic layers. The free magnetic layer includes a first free layer, a second free layer spaced apart from the tunnel barrier layer with the first free layer therebetween, and a spacer layer between the first free layer and the second free layer. The first free layer and the second free layer are antiferromagnetically coupled to each other by the spacer layer, and each of the first free layer and the second free layer has a magnetization direction substantially perpendicular to an interface between the free magnetic layer and the tunnel barrier layer. A thermal stability of the free magnetic layer is in a range of 0 to 15.