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[Display omitted] In recent years, enormous efforts have been made to identify and manipulate the exotic electrical and magnetic properties at a two-dimensional (2D) limit of various exciting materials. The spin–orbit coupling (SOC) in 2D van der Waals (vdW) heterostructures opens a fascinating and versatile platform to implement the intriguing quantum-engineered spintronic devices for practical applications. This review comprehensively outlines the modern-era progress of investigating the inherent magnetism of atomically thin 2D materials. Firstly, in this review, the most recent developments of synthesis, characterizations, functionalities, and spin textures in 2D magnetic materials are summarized in detail. Secondly, we conferred the well-known phenomena related to the proximity effect, spin–orbit torque (SOT), spin valve magnetic tunnel junction (MTJ), spin field effect transistor (FET) and magneto memristive-based applications. In addition, we also explored the possible interplay between 2D magnetic materials and associated band topology for spin caloritronics. Finally, we provided our perspective on the recent and upcoming challenges and goals of this promising research area, which leads the 2D magnetic materials to the modern era of energy-efficient quantum computing. [ABSTRACT FROM AUTHOR]

[Display omitted] Spintronics is a growing research field that focuses on exploring materials and devices that take advantage of the electron's "spin" to go beyond charge based devices. The most impactful spintronic device to date is a highly sensitive magnetic field sensor, the spin-valve, that allowed for a 10,000-fold increase in the storage capacity of hard disk drives since it was first introduced in a magnetic recording read head in 1997. In about 2007, the original spin-valve that was based on spin-dependent scattering in metallic magnetic/non-magnetic interfaces evolved to a closely related device in which the essential physics changed to that of spin-dependent tunneling across ultra-thin insulating layers placed between magnetic electrodes, but the basic spin-engineered structure remained largely unchanged. These latter structures were proposed in 1995 as potential memory elements for a magnetic random-access memory (MRAM) and the first demonstration of this possibility was made in 1999. It was only recently (about 2019) that MRAM became a mainstream foundry technology. Compared with most conventional charge based electronic devices, spintronic devices have the advantage of non-volatility, low-power consumption, and scalability to smaller dimensions. For these reasons, spintronic devices are highly attractive for next-generation information memory-storage and are promising for advanced applications such as in-memory computing. Furthermore, spintronics allows for a unique high capacity, non-volatile, solid-state memory-storage device that relies on devices that can store multiple digital bits in the form of a series of chiral domain walls that are moved at high-speed using nanosecond long current pulses along magnetic nanowires. These devices also enable synaptic functionalities in neuromorphic computing and are therefore, potential hardware candidates for artificial intelligence. In this review article, recent advances in multi-state spintronic devices are discussed. The review starts with an introduction followed by a discussion on using domain-walls for achieving multiple states for memory and neuromorphic computing. In the next section, achieving multiple levels based on domain nucleation are discussed. Subsequent discussions review the use of magnetic pillars, and other schemes for achieving high-density memory. The prospects of spintronic devices in neuromorphic computing for artificial intelligence (AI) are also presented. The outlook and directions for new research are provided at the end. [ABSTRACT FROM AUTHOR]

The development of advanced magnetic tunnel junctions with a footprint in the single-digit nanometer range can be achieved using structures with an elongated and composite ferromagnetic free layer. Using advanced modeling techniques, we investigated the back-hopping effect in ultra-scaled STT-MRAM devices, defined as the unintended switching of the last part of the free layer, leading to an undesired magnetization state of the free layer. To understand the switching of the free layer, the torque acting on both parts of the composite-free layer must be studied in detail. A reduction in the size of MRAM components to increase the memory density may lead to back-hopping. However, the observed back-hopping effect can also be exploited for the realization of multi-level cells. For this purpose, we have carefully investigated the switching behavior of a device with several tunnel barrier interfaces and a few nanometers in diameter. Our studies on ultra-scaled STT-MRAM devices highlight the significant back-hopping effect which, when harnessed, can enable multi-bit cells with four distinct states, enhancing storage and functionality. These insights are pivotal for the design and optimization of future miniaturized spintronics devices. [ABSTRACT FROM AUTHOR]

Exploring the controlled magnetic anisotropy energy (MAE) in two-dimensional (2D) ferromagnets is an essential step towards the emergent magnetic tunnel junctions (MTJs) with robust storage stability and low-power consumption. In addition to the transitional charge doping method, we propose that stacking 2D ferromagnet 1T-CrTe 2 with electrides substrate can achieve not only the high interfacial charge transfer up to 5.24×1014 cm−2 and but also efficient modification of magnetic behaviors via interfacial engineering. Employing first-principles calculations, we show that the 1T-CrTe 2 /Ca 2 N(Y 2 C) heterostructures exhibit a significant reduction in MAE with a spin reorientation. Notably, the synergistic effect of internal charge transfer, external strain and charge doping shows a significant influence on the magnetic behaviors of the bilayer structures, enabling an efficient modulating of their MAE with distinct dependences. We elucidate that the underlying mechanism is the synergistic effect induced alteration of the spin-polarized p x and p y states on the Te atom located at the interfaces, which in turn changes the competitive spin-orbit coupling (SOC) contributions to the MAE. These findings provide a practical path toward the controllable MAE in 2D ferromagnets, and make the proposed heterostructures promising candidates for emergent spintronic devices. • 1T-CrTe 2 /Ca 2 N and 1T-CrTe 2 /Y 2 C heterojunctions were investigated for tunable 2D ferromagnetism. • The synergistic effect of interfacial charge transfer and strain was investigated for controlling the MAE of 1T-CrTe 2. • Significant tuning of MAE arises from the altered electron occupancy of the interface Te-derived p -orbitals. [ABSTRACT FROM AUTHOR]

Replacing the ferromagnet with ferrimagnet (FiM) in the magnetic tunnel junction (MTJ) allows faster magnetization switching in picoseconds. The operation of a memory cell that consists of the MTJ and a transistor requires reversable magnetization switching. When a constant voltage is applied, we find that the spin-transfer torque can only switch the FiM-MTJ from parallel to antiparallel state. This stems from the small switching window of FiM and the dynamic resistance variation during the magnetization switching. We find the resulting current variation can be suppressed by reducing the magnetoresistance ratio. Furthermore, we demonstrate that the switching window can be expanded by adjusting the amount of Gd in FiM. We predict that the polarity of both switching current (J c,switch) and oscillation current (J c,osc) reverses at the angular momentum compensation point but not the magnetization compensation point. This anomalous dynamic behavior is attributed to the different physical nature of magnetization switching and oscillation in FiM, which must be considered when designing FiM-based MRAM. [ABSTRACT FROM AUTHOR]

• FeMn electrodes were used to create molecular spintronics devices with MTJs as test beds. • SMM molecules showed different responses near room temp and below Neel temp on 10,000 MTJs. • KPAFM revealed changes in surface potential after spin channels were established in MTJs. • MTJMSD enabled integration of molecular channels with various stable metal electrodes. The integration of single-molecule magnets (SMMs) into magnetic tunnel junctions (MTJs) offers significant potential for advancing molecular spintronics, particularly for next-generation memory devices, quantum computing, and energy storage technologies such as solar cells. In this study, we present the first demonstration of SMM-induced spin-dependent properties in an antiferromagnet-based MTJ molecular spintronic device (MTJMSD). We engineered cross-junction-shaped devices comprising FeMn/AlO x /NiFe MTJs. The AlO x barrier thickness where the exposed junction edges meet was comparable to the SMM length, facilitating the incorporation of SMM molecules as spin channels for spin-dependent transport. The SMM channels enabled long-range magnetic moment ordering around molecular junctions, which were precisely engineered via fabrication processes. The SMM, composed of a [Mn 6 (μ 3 -O) 2 (H 2 N-sao) 6 (6-atha) 2 (EtOH) 6 ] (H 2 N-saoH = salicylamidoxime, 6-atha = 6-acetylthiohexanoate) complex, featured thioester groups at the ends that upon hydrolysis they form bonds with the magnetic electrodes. SMM-treated junctions demonstrated a significant current enhancement, reaching up to 7 μA at an input voltage of 60 mV. Furthermore, SMM-doped junctions exhibited current stabilization in the μA range at lower temperatures, whereas the bare electrodes showed current suppression to the picoampere range. Magnetization measurements conducted at 55 K and 300 K on pillar-shaped devices revealed a reduction in magnetic moment at low temperatures. Additionally, Kelvin probe atomic force microscopy (KPAFM) measurements confirmed that SMM integration transformed the electronic properties over long ranges.These findings are attributed to the spin channels formed between magnetic metal electrodes, which enhance spin polarization at each magnetic electrode. Our research highlights the potential of using antiferromagnetic materials, characterized by minimal stray fields and zero net magnetization, to transform MTJMSD devices. [ABSTRACT FROM AUTHOR]

• Discovery of new half-metal nanoribbons. • The spintronic devices exhibit a perfect spin-filtering phenomenon. • The spintronic devices exhibit extremely high TMR. Since the successful synthesis of α-phosphorus carbide (α-CP) using carbon doping technology, α-CP has exhibited excellent carrier mobility and anisotropy at room temperature, underscoring its potential for spintronic applications. The application of CP in spintronic devices is limited due to its lack of magnetism. Effective magnetic injection in non-magnetic semiconductors can typically be achieved by doping with magnetic atoms. In this study, we calculated the electromagnetic properties of transition metal (TM) atoms adsorbed at different positions on α-CP using first principles. Notably, we found that α-CP nanoribbons adsorbed with Fe and Mn atoms of a specific width exhibit stable half-metallicity. We discovered that α-CP nanoribbons adsorbed with Fe and Mn atoms of a specific width exhibit stable half-metal properties and design magnetic tunnel junctions with half-metallic Fe_H12 and Mn_H12 adsorption structures. The results show that Mn_H12 and Fe_H12 devices exhibit a highly efficient spin filtering effect, with a TMR as high as 5521%. These findings provide theoretical guidance for the application of CP-based spintronic devices. [ABSTRACT FROM AUTHOR]

• Utilizing telegraphic switching signal of MTJ for stochastic computing. • Roberts Cross operator designed by stochastic computing. • Roberts cross operator realized by simple logic using MTJ. • Edge detection results differ based on generated bit-stream length. A hardware method for image edge detection is proposed by using stochastic behavior of magnetic tunnel junction. Telegraphic switching property of magnetic tunnel junction is employed for obtaining random bits which allows constructing a circuitry of a probabilistic bit-stream generator for stochastic computing. By applying the Roberts cross operator, we develop a stochastic way for edge detection with approximation of image gradient, which successfully conducts the role of image edge detection. Different edge detection results for different bit-stream lengths are shown in order to suggest the optimal bit-stream length for operation. [ABSTRACT FROM AUTHOR]

It has been proposed recently that 1D hybrid nanoobjects consisting of alternating double carbon chains and polycyclic carbon regions can be obtained from graphene nanoribbons of alternating width by electron irradiation. Here, based on density functional theory calculations, we show that magnetic and electronic properties of such nanoobjects can be changed dramatically by modifying the chain length and edge structure of polycyclic regions and this opens wide possibilities for spintronic applications. Nanoobjects composed of polycyclic regions with dangling bonds and even chains are found to behave as magnetic semiconductors that can generate spin-polarized currents. Band gaps of nanoobjects with odd chains change considerably upon switching between magnetic states making them promising for magnetic tunnel junctions. We also demonstrate that use of a hybrid exchange–correlation functional is important to properly describe stability of magnetic states, band gaps and synergistic effects of nanoobject components leading, for example, to magnetism in even chains. • Nanoobject properties strongly depend on chain parity and polycyclic region edges. • Nanoobjects with even chains and unsaturated edges can be magnetic semiconductors. • Nanoobjects with odd chains hold promise for magnetic tunnel junctions. • Stable magnetism in observed in odd chains and at unsaturated polycyclic region edges. • Even chains in nanoobjects can be magnetic because of non-local synergistic effects. [Display omitted] [ABSTRACT FROM AUTHOR]

• Electronic and atomic interactions inside the molecule impacted two ferromagnetic electrodes connected to the molecule. • Interaction of the electron with the nearest atom and neighboring electrons within the molecule Impacted the devices. • Biquadratic coupling between the neighboring atoms inside the molecule significantly impacted the spintronic device. Molecular spintronics devices (MSD) offer significant potential for next-generation computing and memory applications. In our prior experimental studies, we have utilized cubic Octametallic Molecular cluster composed of iron and Ni atoms without understanding different spin states the molecule can attain when covalently bonded with the two ferromagnetic electrodes. This study investigates the behavior of normalized molecular spin (S m) alongside three key variables: total system magnetization (M), molecular magnetization (M m), and free electron magnetization (F m), which represents the free electron component of local molecular magnetization, under various thermal energies. Using Monte Carlo simulations (MCS), we analyze these parameters within the framework of a magnetic tunnel junction-based molecular spintronics device (MTJMSD) composed of a cubic molecule. The focus is on the dependence of these four variables on biquadratic coupling strength (b m) and exchange couplings between localized atomic spin and nearest free electron spin (J e 0 m) , localized spin and free electron in the vicinity of nearest neighboring atom (J e 1 m) , two nearest free electrons (J eem). All the exchange couplings impact were studied at different thermal energies (kT). Our findings reveal complex interdependencies between these variables. For lower thermal energies (k T ≤ 0.1) , molecular spin decreased sharply with increasing bm , indicating molecular spin settling in low state. At higher thermal energies (k T = 0.5) , a non-monotonic relationship emerges with Sm peaking at intermediate bm values. Additionally, we observe that M increases more significantly with negative exchange couplings between local spin and free electron spin in the vicinity of nearest neighboring local spin at lower kT ; whereas positive magnitude of the same exchange coupling tends to stabilize the lower magnitude of M. Furthermore, the free electron spin (F m) increases with positive Jeem values, plateauing at higher coupling strengths and exhibiting a more gradual increase at higher temperatures. These results highlight the intricate balance between molecular coupling, exchange interactions, and thermal effects, providing critical insights for optimizing the performance and stability of molecular spintronic devices across different thermal energy regimes. [ABSTRACT FROM AUTHOR]

Magnetic tunnel junctions (MTJs) constructed from atomically thin two-dimensional (2D) magnetic materials have attracted great attention in recent years because it meets the requirements of miniaturization and high tunability of next-generation spintronic devices. In this work, we demonstrate that the ferromagnetic semiconductor VS 2 is transformed into a half-metal in VS 2 /MoSSe vdW heterostructure. Based on the heterostructure, we design an in-plane MTJs that comprise a monolayer VS 2 barrier sandwiched between two VS 2 /MoSSe heterostructure electrodes. Through density functional calculations combined with a nonequilibrium Green's function technique, it is found that the tunnel magnetoresistance (TMR) ratio as high as 4.35 × 10 9 % can be achieved. Moreover, the TMR ratio can be tuned by the barrier length, and the maximum value exceeds 10 15 %. These results not only provide a novel route for designing MTJs using 2D ferromagnetic semiconductor material, but also demonstrate the great importance of vdW heterostructures in the design of spintronic devices. [Display omitted] [ABSTRACT FROM AUTHOR]

• Graphether is a semiconductor material that exhibits favorable characteristics for doping processes. • Stable P-type and N-type semiconductors were successfully synthesized through the process of doping. • A spin switch was devised based on the principle of electron tunneling spin filtering. • The resultant magnetic tunnel junction represents a high-efficiency single-channel spin switch. Spin switches are a fundamental component in the majority of spintronic devices, and have found extensive application in data storage, logical data manipulation, and signal processing. An essential aspect of constructing a spin switch is determining a stable two-dimensional material, which is easy to control and produce. Theoretical studies have shown that graphether is particularly promising due to its exceptionally high melting point and outstanding air stability. The band structure can be modified by doping, making it an important material for spin switch applications. In this paper, we have calculated the electromagnetic properties of doped graphether by first principles. Then we select a modified graphether with P-type and N-type doping configurations to construct magnetic tunnel junctions (MTJ). The results show that the MTJ exhibits perfect highly efficient spin switch as a result of spin reversal induced by spin-transfer torque (STT). In addition, our designed MTJ shows a remarkable rectification effect and spin filtering effect (SFE). According to our calculations, the modified graphether materials also show promise as two-dimensional spintronics materials. [ABSTRACT FROM AUTHOR]

• In this work, we studied MTJs based on thin film and complete Heusler alloy as electrodes and WSe 2 2D material as tunneling barrier. • The proposed MTJ exhibits advantages over conventional materials like transition metals (Fe, Co, Ni) with metal oxides (MgO, Al 2 O 3). • The obtained TMR values of the proposed MTJ with a single layer of WSe 2 is as high as 1.75 lakh %, which is a very high value (order of 5). This paper presents a Magnetic Tunnel Junction (MTJ) based on Co 2 FeAl Heusler alloy and 2D material WSe 2 with an enhanced tunnelling magneto-resistance (TMR). Our study is inspired by recent investigations of 2D materials and Heusler alloys. By employing static Density Functional Theory (DFT) simulations coupled with Non-Equilibrium Green's Function (NEGF) transport models, we evaluate conductance properties in Co 2 FeAl/WSe 2 /Co 2 FeAl MTJ. The half metallicity of Co 2 FeAl and quantum confinement properties of WSe 2 are compatible, which enhances the TMR of MTJ. [ABSTRACT FROM AUTHOR]

Emerging nonvolatile magnetoresistive random access memory exhibits high endurance and long data retention compared to flash memory. Additionally, devices with double spin torque magnetic tunnel junctions (dsMTJ) featuring two magnetic reference layers demonstrate enhanced torques, fast switching, and reduced switching currents. To accurately model these devices, we adopt a coupled spin and charge transport approach allowing to describe spin-transfer torques in metallic spin valves and magnetic tunnel junctions on equal footing. Our findings indicate the critical influence of metallic non-magnetic spacers (NMS) properties separating the free layer from the second reference layer on the switching speed improvement in dsMTJ devices. • Coupled charge, spin and magnetization dynamics. • Spin torques in novel STT-MRAM sturcture, double spin-torque MTJ (dsMTJ). • Additional torque in dsMTJ due to second RL. • Two times faster switching compard to regular MTJs. [ABSTRACT FROM AUTHOR]

The tunneling magnetoresistance (TMR) magnetic sensor offers numerous advantages, including high response speed, strong anti-interference capability, high reliability, and ease of integration. Despite the challenges associated with generating high-frequency alternating magnetic fields, we have investigated the frequency response characteristics of a self-developed TMR magnetic sensor (TMR-MS) with highly sensitive properties of approximately 430mV/V/Oe and a detection limit of 340 pT/Hz 1 2 . Through experimental testing for frequency response, our TMR-MSs demonstrate exceptional fast response capabilities across temperatures ranging from -30 °C to 50 °C. These experimental results highlight the significant potential of TMR-MS with highly sensitive properties for industrial applications. • TMR-MS has numerous advantages: Fast, reliable, anti-interference, easy integration. • Highly sensitive: 430 mV/V/Oe. Detection capability: 340 pT/Hz 1 / 2. • Robust performance: TMR-MS maintains fast response (-30 °C to 50 °C). • Industrial potential: Highly sensitive TMR-MS suits demanding environments. [ABSTRACT FROM AUTHOR]

A new series of double half-Heusler (DHH) alloy Cr 2 FeCoZ 2 (Z = As, Ge, S, P) are investigated by using the non-equilibrium Green's function in combination with the first-principles calculations. The calculations on magnetism reveal that these Cr-based DHH alloys are ferrimagnets due to the antiparallel magnetic coupling between Cr and Fe (Co). The electronic structure calculations of the Cr-based DHH alloys reveal half-metallicity, and Cr 2 FeCoAs 2 possesses the largest spin-down gap of 1.181 eV. Within the c/a ranges from 1.60 to 2.52, Cr 2 FeCoAs 2 maintains its 100 % spin-polarization, and the changes in total and spin-resovled atomic magnetic moment are negligible, showing a stable half metallicity and magnetism against the tetragonal distortion. Futhermore, the transport properties are investigated by constructing the Cr 2 FeCoZ 2 /GaAs/Cr 2 FeCoZ 2 magnetic tunnel junction (MTJ) model. By changing the magnetic arrangement of the left and right electrodes into antiparallel configuration, the capability of transportation in both spin channels is significantly limited. Conversely, by modulating the magnetic arrangement of the left and right electrodes into parallel configuration, the transportation of electrons in spin-up channel is exceptionally strong while that of the spin-down channel is severely impeded. The Cr 2 FeCoAs 2 /GaAs/Cr 2 FeCoAs 2 MTJ owns the highest tunneling magnetoresistance (TMR) ratio of ∼7.42 × 108 %, indicating that Cr 2 FeCoAs 2 is the most promising candidate for high performance spintronic devices. • A series of Cr-based double half-Heusler alloy is confirmed to possess stable half-metallicity. • The calculated TMR ratio of the Cr 2 FeCoAs 2 /GaAs/Cr 2 FeCoAs 2 MTJ is up to ∼7.42 × 108 %. [ABSTRACT FROM AUTHOR]

[Display omitted] Chiral magnetic skyrmions are topological swirling spin textures that hold promise for future information technology. The electrical nucleation and motion of skyrmions have been experimentally demonstrated in the last decade, while electrical detection compatible with semiconductor processes has not been achieved, and this is considered one of the most crucial gaps regarding the use of skyrmions in real applications. Here, we report the direct observation of nanoscale skyrmions in CoFeB/MgO-based magnetic tunnel junction devices at room temperature. High-resolution magnetic force microscopy imaging and tunneling magnetoresistance measurements are used to illustrate the electrical detection of skyrmions, which are stabilized under the cooperation of interfacial Dzyaloshinskii–Moriya interaction, perpendicular magnetic anisotropy, and dipolar stray field. This skyrmionic magnetic tunnel junction shows a stable nonlinear multilevel resistance thanks to its topological nature and tunable density of skyrmions under current pulse excitation. These features provide important perspectives for spintronics to realize high-density memory and neuromorphic computing. [ABSTRACT FROM AUTHOR]

The switching current requirement of magnetic tunnel junction (MTJ) in STT MRAM is highly asymmetric. This results in unnecessary higher power dissipation due to excess write current in one direction. To tackle this issue, we present a novel STT MRAM cell that utilizes the trimmed fin asymmetric FinFET (A-FinFET) as an access device, which has an impressive asymmetry in the bidirectional current and smaller gate capacitance compared to the symmetric FinFET device. Our approach begins with the development of a SPICE model for the A-FinFET, achieved by calibrating the BSIM-CMG model to replicate the characteristics of the A-FinFET. Further, it is used to evaluate the performance of STT MRAM using a comprehensive analysis from the cell to the architecture level, employing HSPICE and NVsim tools. The findings indicate significant enhancements with the proposed design, leading to a remarkable 18 % reduction in power consumption without compromising area. Additionally, the effective area of wordline drivers is reduced by 11 % compared to the symmetric device implementation. • A novel STT-MRAM cell employing trimmed fin asymmetric FinFET (A-FinFET) as an access device. • Calibration of the BSIM-CMG model to replicate the characteristics of the A-FinFET. • Comprehensive analysis from the cell to the architecture level, employing HSPICE and NVsim tools. • Remarkable 18 % reduction in power consumption without compromising area. • Effective area of word line drivers is reduced by 11 % compared to the symmetric device implementation. [ABSTRACT FROM AUTHOR]

• High B2 ordering parameter was observed in Co 2 FeAl x Si 1– x thin films. • Magneto-crystalline anisotropy constant K 1 changed as Al component x increased in Co 2 FeAl x Si 1– x thin films. • Magneto-crystalline anisotropy constant K 1 crossed K 1 = 0 line at around x = 0.33. A tunnel magnetoresistance (TMR) sensor is a highly sensitive magnetic sensor workable at room temperature. To achieve smaller magnetic field detection, both a high TMR ratio and small magnetic anisotropy of the free layer are required. In this study, we developed single crystalline Co-based Heusler alloy Co 2 FeAl x Si 1- x films as the free layer of TMR sensors and systematically investigated their crystalline and magnetic properties. The magnetic tunnel junction (MTJ) with these alloys is a promising device for highly sensitive TMR sensors due to their half-metallicity. We evaluated the B2 and L2 1 ordering parameters S B2 and S L21. S B2 was above 80 % for all the samples and S L21 was 48 % at a maximum, which indicates that all the samples exhibit half-metallicity. In addition, we evaluated their first magneto-crystalline anisotropy constant K 1 from magnetization curves. K 1 changed from positive to negative as Al component x increases and K 1 was about 1200 erg/cc at x = 0.33. These results indicate that Co 2 FeAl x Si 1- x films around x = 0.33 have a good candidate for the free layer of TMR sensors because of their half-metallicity and small magnetic anisotropy. [ABSTRACT FROM AUTHOR]

Magnetic tunnel junctions are the core component of spintronic devices, and good magnetic tunnel junctions require high tunnel resistance, which is determined by the spin polarization of the thin films of ferromagnetic layers that make up their structure. Therefore, the design of ferromagnetic films with high spin polarization is a current research hotspot in this field. In the current study, we taken the half-metallic CrYCoAl as an object, and studied the influence of surface effect on the half-metallic behavior. Especially, we constructed the CrYCoAl (100), (110), and (111) surfaces to study their stability, electronic and magnetic properties. Results show that the YY and YAl (100) surfaces, and Co (111) surface retain the half-metallic behavior and structural stability of bulk, which provide a basis for CrYCoAl application as a thin films in magnetic tunnel junctions thus, they are likely to be used in the spintronic devices. • Stability of CrYCoAl (100), (110) and (111) surfaces are estimated by their phase diagrams. • Atomic relaxation and surface roughness are discussed. • Electronic and magnetic properties of CrYCoAl (100), (110) and (111) surfaces are studied. • The YAl and YY (100), and Co (111) termination surfaces maintain the half-metallic nature of bulk CrYCoAl. [ABSTRACT FROM AUTHOR]

• Thermoelectric effects of resonant-tunneling MTJs (RTMTJs) are investigated theoretically. • There are β-Ga 2 O 3 , ZnO and a non-magnetic metal as quantum well between the MgO barriers. • Improvements in the thermoelectric features are achieved in the RTMTJs based on β-Ga 2 O 3. A study was conducted to investigate thermoelectric effects (TEEs) in resonant-tunneling magnetic tunnel junctions (RTMTJs) featuring wide-bandgap semiconductors such as ZnO and β-Ga2O3, along with a non-magnetic metal spacer. The transmission function was determined using the non-equilibrium Green's function method within a tight-binding model. Significant enhancements in TEEs were observed for the β-Ga2O3 semiconductor compared to other materials, indicating its potential applicability in the emerging field of β-Ga2O3 spincaloritronics. [ABSTRACT FROM AUTHOR]

• The operation stability of PMA structures with different HMs were investigated. • The appropriate HM and structure can enhance the thermal stability of PMA. • The thermally robust PMA was obtained in the Co-rich CoFeB composition. For magnetic sensor and magnetic random access memory, the thermally tolerant need to be improved at a relatively high operation temperature. In this work, the correlations between the thermal stability and perpendicular magnetic anisotropy films with different heavy metal layers, structures and CoFeB compositions were investigated in details. It was found that the thin films adopting W or Mo heavy metal layer in the bottom structure, and the thin films adopting Mo heavy metal layer in the top structure exhibit a relatively good operation stability, no matter what the CoFeB composition is. Moreover, the thermally robust perpendicular magnetic anisotropy was obtained in the CoFeB with a relatively large Co atomic composition. According to the element distribution states analysis and oxidation conditions at CoFeB/MgO interface, the reasons are attributed to the structural- and composition-dependent Fe-O bonding. This research helps to design and optimize the ultra-low-power and thermally stable magnetic devices based on the suitable heavy metal layers, structures, and CoFeB compositions. [ABSTRACT FROM AUTHOR]

• A strategy to realize nonvolatile magnetization reversal is proposed based on electric field control of interlayer coupling. • The dependence of interlayer coupling energy on electric field strength follows a continuous odd function in mathematics, guaranteeing the nonvolatility. • The feasibility of this strategy is demonstrated by a MnBi 2 Te 4 / h -BN/Fe 3 GaTe 2 / h -BN/MnBi 2 Te 4 junction. Achieving electric field control of nonvolatile magnetization reversal in van der Waals magnetic tunnel junctions (vdW MTJs) is of paramount importance for nanoscale spintronic devices with ultralow-power consumption and high-density storage. Here, a new and universal design strategy is proposed to realize nonvolatile magnetization reversal, which is based on electric field control of interlayer coupling. The nonvolatility benefits from the proposed special principle of vdW MTJ, in which the dependence of interlayer coupling energy on electric field strength follows a continuous odd function in mathematics. The feasibility of proposed strategy is proved by the MnBi 2 Te 4 / h -BN/Fe 3 GaTe 2 / h -BN/MnBi 2 Te 4 junction. The magnetization state of Fe 3 GaTe 2 can be reversed 180° by changing electric field directions. Moreover, the magnetization states can be preserved after removing electric field, demonstrating the nonvolatile magnetization reversal. Therefore, the present strategy provides an alternative approach to realize electric control of nonvolatile magnetization reversal in vdW MTJs for next-generation spintronic devices. [ABSTRACT FROM AUTHOR]

The CoFeTiSi compound is an experimentally existing half-metallic ferromagnetic Heusler compound with a Curie temperature higher than room temperature. By replacing the Si atom with Al, we can obtain a narrow bandgap semiconductor CoFeTiAl. The lattice mismatch between CoFeTiSi and CoFeTiAl is very small, which serves as motivation for constructing a CoFeTiSi/CoFeTiAl/CoFeTiSi magnetic tunnel junction. In this junction, CoFeTiSi and CoFeTiAl are used as electrode and barrier layers, respectively. The optimal device structure can be achieved simply by replacing the Si atoms in the barrier region with Al atoms. Through the use of a b i n i t i o atomic thermodynamics, we have found that this device structure is more stable compared to a junction formed by the same two compounds with an alternative interface. Transport calculations reveal that this junction can achieve a high tunneling magnetoresistance ratio at room temperature and exhibit a large transmission coefficient. These characteristics make the CoFeTiSi/CoFeTiAl/CoFeTiSi magnetic tunnel junction an ideal candidate for future spintronic applications. [Display omitted] • An all-Heusler MTJ which can achieve a high TMR at RT is proposed theoretically. • The stable normal atomic order at the interface minimizes the interface disorder. • The MTJ device achieves a high T P ↑ that is easy to detect. [ABSTRACT FROM AUTHOR]

Due to the success of artificial intelligence systems in solving complex problems, these systems have been investigated in many applications. There is an increasing demand for these systems in many new applications. The XNOR-Net, a binary neural network, is a promising candidate for implementing these systems in devices with limited power and hardware resources. Efficient hardware implementation of XNOR-Nets is critical and has been widely investigated in recent research. In this paper, a resource-sharing gate and architecture and a task-scheduling gate and architecture have been proposed. To reduce power consumption, the proposed nonvolatile logic-in-memory gates are designed based on the magnetic tunnel junction (MTJ) and carbon nanotube field-effect transistor (CNTFET) devices. Using the proposed resource-sharing gate for hardware implementation of XNOR-Net minimizes the number of flip-flops, power consumption, PDP, and area by at least 75%, 75%, 60%, and 42%, respectively, as compared to its state-of-the-art counterparts. Also, using the proposed task-scheduling design to implement the XNOR-Net on 2, 4, and 8 datasets, the power consumption is reduced by at least 24%, 54%, and 65%, respectively, compared to its state-of-the-art counterparts. [ABSTRACT FROM AUTHOR]

• This article proposes new logic gates based on four-channel magnetic cell (mcell) with new magnetic logic (mlogic) called multilevel cell gate (MLC Gate). • In order to design the proposed gate circuit, MLC Gate is used magnetic gate (MGate) basic structure to reduce heat losses, Spin Based Electronic Gate (SBEG) structure to reduce the number of mcells and create a neural network, and finally the multi-level property of voltage-controlled spin orbit torque-memory (MV-SOTM) cells to reduce energy consumption. • mcell with mlogic proposed in this article has only four bases. The two writing paths of the mcell are composed of two layers with constant magnetization, which are made in two opposite directions to align the direction of the electric current with the direction of the domain wall field. The two reading paths of the mcell are made of two MTJ magnetic cells in series. So that the variable ferromagnetic layer of these two MTJ cells is isolated under the influence of the domain wall field by an insulating layer of Mgo. • One of the advantages of multi leveling mcell is increasing the working frequency to an acceptable value and in this article, the use of the voltage controlled magnetic anisotropy (VCMA) method is well stated to describe the reduction of the critical switching current. Spintronics is an emerging technology for designing logic circuits. The non-volatile logic based on the magnetic tunnel junction (MTJ) cell is a suitable solution to overcome the leakage power problem, which has become a major obstacle for CMOS technology. Here, we introduce a new style of magnetic gate (mGate) logic, which is built by a four-terminal cell. This cell operated by motion of domain wall that is based on spin transfer torque (STT) in a multi-level cell (MLC) structure. To reduce the complexity, a static circuit with a resistive load in ratioed logic style has been used. The use of MLC Gate logic in the static ratioed logic circuit is a suitable solution to reduce the complexity level of structure and power consumption in logic circuits in the field of spintronics. The performance of different magnetic logic gates have been investigated by simulations. The simulation results show that the MLC Gates offer a smaller area and lower power consumption and lower energy in comparison with the previous mGate and magnetic computing in memory. [ABSTRACT FROM AUTHOR]

• Manuscript include advancement in two and three terminal spintronic devices. • Review included artificial neurons based spintronic devices for artificial intelligence. • Yearly development in spintronic technology has been illustrate by flow chart. • The parametric comparisons of MRAM and logic circuit has been included. • Include features of cutting-edge quantum & magnetic tunnel junction. The scaling of metal oxide semiconductor field effect transistors (MOSFETs) for data storing and logic circuit operation has reached a critical point, beyond which further scaling poses various secondary issues. These problems include short channel effects, hot carrier effects (HCEs), and reliability concerns. However, a promising alternative called spintronics has recently emerged as a highly exciting technology. Spintronics considers both the charge and spin of electrons in device operations and offers superior properties compared to MOSFETs. Researchers have reported numerous spintronics devices that exhibit significant potential in memory and logic circuits when integrated with complementary metal oxide semiconductor (CMOS) technology. These devices not only possess excellent scalability but also consume less power than MOSFETs at the nano-scale level. This article aims to provide a comprehensive review of the current state, future prospects, and challenges associated with spintronics devices. [ABSTRACT FROM AUTHOR]

A novel self write-terminated driver is proposed for the hybrid spin transfer torque-magnetic tunnel junction (STT-MTJ)/CMOS circuits based on logic-in-memory (LIM) structure. Using continuous write monitoring mechanism, the novel circuitry completely eliminates the unnecessary flow of write current which abolishes the wastage of write energy in the proposed write driver. Hence, the total energy required for writing process is reduced noticeably by 63.32% in novel write driver compared to the conventional write circuit. Monte-Carlo simulation is then performed by incorporating process and mismatch variations for CMOS and extracted parameters of MTJ. Simulations are also carried out for the proposed write driver, by varying the transistor sizes and supply voltage to analyze its switching probability to obtain safe operating region. Further, the proposed write driver is integrated with hybrid full adder to demonstrate its feasibility in low-power VLSI circuits. [ABSTRACT FROM AUTHOR]

In the last decade, two-dimensional (2D) transition metal dichalcogenides have been introduced with great significance in the spintronic devices for their extraordinary electrical, optical, and spin-dependent properties. In this work, we have fabricated a few-layer molybdenum disulfide (FL-MoS 2) (~6 nm) as a non-magnetic spacer layer in Ni–Mn–In/FL-MoS 2 /Ni–Mn–In magnetic tunnel junction (MTJ) using DC magnetron sputtering. FL-MoS 2 thin film sandwiched between two ferromagnetic shape memory alloy based electrodes exhibit semiconducting behavior, confirmed by current-voltage (I–V) characteristics and temperature dependent resistance measurement. The fabricated MTJ shows spin valve effect in the presence of an external magnetic field. The tunneling magnetoresistance (TMR) has been recorded in 10 K–300 K temperature range. The highest TMR ratio of 0.51% was obtained at a low temperature ~10 K, corresponding to the spin polarization of ~5%. This TMR ratio reduces to a value of 0.032% as the temperature of the device increases up to 300 K, displaying a finite TMR at room temperature. A detailed study of thickness and temperature-dependent magnetization versus magnetic field (M − H) hysteresis loops of Ni–Mn–In thin films has been performed to understand the complex TMR behavior. The present study paves the way for the use of sputtered FL-MoS 2 and ferromagnetic shape memory alloy in ultrafast spintronics for advanced magnetic devices application. [ABSTRACT FROM AUTHOR]

This paper explores non-volatile cache memories implemented by spin-transfer torque magnetic random access memories (STT-MRAMs) based on state-of-the-art perpendicular magnetic tunnel junctions (MTJs) and FinFETs. The use of double-barrier MTJs with two reference layers (DMTJs) is benchmarked against solutions relying on single-barrier MTJs (SMTJs) at different technology nodes (from 28-nm down to 20-nm). Our study is carried out through a cross-layer simulation platform, starting from the device- up to the system-level. Our results point out that, thanks to the reduced switching currents, DMTJ-based STT-MRAMs allow decreasing write access time of about 63% as compared to their SMTJ-based counterparts. This is achieved while assuring reduced energy consumption under both write (−42%) and read (−28%) accesses, lower area occupancy (−40%) and smaller leakage power (−25%), at the only cost of worsened read access time. This makes DMTJ-based STT-MRAM a promising candidate to replace conventional semiconductor-based cache memory for the next-generation of low-power microprocessors with on-chip non-volatility. • STT-MRAMs for cache applications based on p-MTJ and FinFET devices are investigated. • DMTJ-based STT-MRAMs are benchmarked against their SMTJ-based counterparts. • Our study is performed by a cross-layer simulation platform, from the device- up to the system-level. • DMTJ-based STT-MRAMs prove to be credible candidates for replacing SRAM-based caches in low-power applications. [ABSTRACT FROM AUTHOR]

Some of the important applications in the field of spintronics are spin current driven logic devices having logic gates and in read heads in the hard disk drives, magnetic random access memory (MRAM) containing non-volatile memory units and extremely complex magnetic sensor. In spintronic applications, a magnetic tunnel junction (MTJ) is considered the back bone of all such devices. With this motivation, in present study we have predicted very low resistance area (RA) product value and high tunnel magneto resistance (TMR) of two designed MTJs by using full Heusler alloys (FHA) Co 2 TiZ (Z = Ge, Si) as electrode and MgO as barrier layer. These used half metallic (HM) Heusler alloys (HA), have been investigated using Wien2K code, via primary standard calculations and studied electronic and magnetic properties followed by structural and magnetic phase stability. Spin based band structure along with density of state (DOS) profiles are determined by considering both generalized gradient approximation (GGA) + modified Becke–Johnson functional (mBJ) functional and GGA potentials. For the estimation of the Curie temperature (T c) mean field approximation (MFA) was considered. After determining physical properties of considered FHAs, spin polarised transport properties are calculated by using PWCOND code embedded in Quantum ESPRESSO (QE) for designed MTJs and obtained extremely low resistance-area product (RA) product and a high value of TMR which is found very suitable for spintronic device applications. • Structural study for four different Wyckoff positions. • Comparison of GGA and GGA + mBJ results for energy gap. • Curie temperature measurements by mean field approximation. • Transport properties designed MTJ with MgO barrier. • Calculation of TMR and RA product. [ABSTRACT FROM AUTHOR]

We develop perpendicularly magnetized magnetic tunnel junctions (MTJs) consisting of a CoFeB/Mg 40 Fe 10 O 50 (MgFeO)/CoFeB multilayer. The use of MgFeO yields a substantial improvement in the flatness of the MTJ film stack compared with conventional MTJ films using MgO as a tunnel barrier layer, and a 1.7 times enhancement in the perpendicular magnetic anisotropy energy is obtained for the ultrathin CoFeB layer deposited on the MgFeO layer. Nanostructural analysis combined with elemental distribution mapping reveals the formation of highly (001)-oriented MgFeO in the as-deposited MTJ film, and the crystalline MgFeO layer effectively inhibits diffusion of B atoms from the CoFeB layers through the tunnel barrier layer during the post-annealing process. Accordingly, the MgFeO-MTJ exhibits exceptional stability against high temperature annealing, and a large tunnel magnetoresistance ratio of 235% is demonstrated in MTJ nanopillar devices after annealing at 400 °C. Ferromagnetic resonance measurements also reveal a reduced magnetic damping in the MgFeO-MTJs owing to the improved uniformity in the CoFeB layer. The present experimental results will facilitate the development of magnetoresistive memory devices with increasing memory density and higher energy efficiencies. [Display omitted] [ABSTRACT FROM AUTHOR]

• The pristine bilayer NiBr 2 is an A-type antiferromagnetic semiconductor, which becomes a ferromagnetic half-metal under electron doping. • Li intercalation also can induce a similar magnetic transition along with a electron transition from the semiconductor to half-metal. • We design a magnetic tunnel junction based on bilayer NiBr 2 , showing a giant tunnel magnetoresistance up to 1.7 × 1011 100%. Two-dimensional bilayer materials, such as twisted bilayer graphene, are promising for device applications due to their tunable and controllable electronic properties. Here, we propose to modify the magnetic properties of the bilayer NiBr 2 with electron doping using first-principles calculations. Our results show that the pristine bilayer NiBr 2 is an A-type antiferromagnetic (AFM) semiconductor, which becomes a ferromagnetic (FM) half-metal under electron doping. Such transition is caused by lower electronic state occupation at the band edge. Instead of electrostatic doping, the intercalation of the alkali metal lithium can induce the same magnetic phase transition. Finally, a magnetic tunnel junction based on bilayer NiBr 2 is designed, showing giant tunnel magnetoresistance up to 1.7 × 1011 %. These results offer fresh perspectives on the application of antiferromagnetic bilayer materials for spintronic devices. [ABSTRACT FROM AUTHOR]

• A novel magnetic sensor with sub-10 nm thickness and GHz operation is proposed. • Lateral spin valve terminates in a magnetic tunnel junction with a SAF free layer. • Interaction of interlayer dipole & exchange couplings with STT switching examined. • SNR above 20 dB has been achieved with current density of 107 A/cm2 or less. We present a new magnetic sensor design using a lateral spin valve (LSV) structure that features a sensing end less than 10 nm thick, making it suitable for integration with nanoscale devices. Shot noise reduction and signal-to-noise ratio (SNR) improvement under gigahertz operation are expected for our design. The spin detection part of the LSV forms a magnetic tunnel junction (MTJ) beneath the aluminum channel. We propose to replace the single layer ferromagnet in the spin detection part of the LSV with a synthetic antiferromagnetic structure: this facilitates spin-transfer torque (STT) induced magnetization switching. Macrospin simulation shows that interlayer magnetic dipole coupling helps STT switching while interlayer exchange coupling hurts, owing to their different precession symmetries in the out-of-plane direction. It also shows that SNR > 20 dB can be achieved for a pseudorandom binary sequence with a minimum bit length 0.5 ns. [ABSTRACT FROM AUTHOR]

Ta/CoFeB/MgO/Ta multilayer known as the fundamental building block for magnetic tunneling junctions, has been studied for decades. However, its thermostability is normally less than 300 °C, which cannot meet the requirements for subsequent semiconductor processes. In this study, buffer layers of {Pt(t)/Ta(t)} n superlattices were introduced into CoFeB/MgO/Ta multilayers grown by magnetron sputtering. The growth period n and the single layer thickness t in the superlattice have been systematically explored. And it is found that the sample can maintain distinct perpendicular magnetic anisotropy (PMA) even after a 440 °C post-annealing treatment at n = 3 and t = 1.5 nm. This has been attributed to that the superlattice buffer layer might serve as a diffusion barrier, reducing Ta atoms from diffusing into the CoFeB/MgO interface. Less Ta at the interface results more FeO x formed and enhances the hybridization of Fe 2p and O 3d orbitals which increases the thermostability of PMA. This suggests that superlattice buffer layer provides a new approach to improve the materials' thermostability. • The {Pt(t)/Ta(t)} n superlattices were introduced into CoFeB/MgO/Ta multilayers grown by magnetron sputtering. • The {Pt(t)/Ta(t)} n superlattice can improve the thermostability of the films' PMA up to 440 °C. • The periodic structure reduces diffusion of Ta, enhances the orbital hybridization of Fe and O. [ABSTRACT FROM AUTHOR]

• In this paper, TMR-superconducting composite magnetic sensors have been successfully fabricated by sputtering. • Compared with the traditional bonding method, the distance between the superconducting loop and TMR in this paper is further reduced. • Compared with the traditional bonding device, the TMR-superconducting composite magnetic sensor prepared by sputtering has better weak magnetic field detection performance. The tunneling magnetoresistance (TMR) effect, utilizing the CoFeB/MgO/CoFeB magnetic tunnel junction (MTJ) structure, has seen a surge in research interest owing to its pronounced sensitivity to magnetic fields. However, advancements in TMR technology have plateaued in recent times. In response, this study explores the integration of TMR with superconductivity to form a TMR-superconducting composite magnetic sensor, aiming to amplify the external magnetic field effect and improve sensor performance. Such sensors offer significant promise for applications in detecting feeble magnetic fields due to their compact dimensions, minimal energy consumption, and exceptional magnetic field resolution. Despite their potential, manufacturing challenges persist. This paper focuses on the meticulous fabrication of the TMR's critical thin film layer and its subsequent patterning. Moreover, we propose an innovative technique utilizing magnetron sputtering to deposit a niobium (Nb) layer atop the TMR structure, followed by intricate patterning to successfully construct a TMR-superconducting composite film. This novel approach importantly diminishes the interspace between TMR and superconducting layers compared to traditional bonding methods, thereby enhancing device performance. Experimental assessments of the device constructed superconducting loops, contrasted with traditional bonding process, demonstrate that sputtering-based sensor exhibit better magnetic field resolution. Consequently, TMR-superconducting composite sensors realized via the sputtering technique hold distinct advantages in weak magnetic field detection. [ABSTRACT FROM AUTHOR]

Fe-doped transition metal disulfides can be prepared by in situ substitutional doping, and the Fe-doped WS 2 (Fe:WS 2) was predicted to be a 2D ferromagnetic half-metal with high Curie temperature. Ferromagnetic half-metal may enlarge the tunneling magnetoresistance (TMR) in magnetic tunneling junctions. Herein, we constructed the Fe:WS 2 /WS 2 /Fe:WS 2 in-plane tunneling junctions with narrow WS 2 barrier and studied the spin-polarized quantum transport based on the density functional theory combined with non-equilibrium Green's function. The calculated TMR can be as large as 107, which is rarely available as far as we know. Besides, the spin-polarized current oscillates with the bias voltage and perfect spin filtering effect can still be found even at nonzero bias. The nonequilibrium quantum transport can be explained by the changes of the spin-dependent transmission spectra at bias voltages. Our calculated results may be helpful for the design and application of WS 2 -based magnetic tunneling junctions in spintronics. [Display omitted] • Planer Fe:WS 2 /WS 2 /Fe:WS 2 junction has giant tunneling magnetoresistance. • The tunneling magnetoresistance can be as large as 10 7 , which is rarely available. • Perfect spin filtering effect can still be found even at nonzero bias. • Ferromagnetic half-metal enhances the magnetoresistance and spin filtering. [ABSTRACT FROM AUTHOR]

As today's CMOS technology is gradually scaling down to its physical limits, emerging technologies are under research as alternatives in the future, such as carbon nanotube, magnetic tunneling junction, memristor. Among them, memristor is a promising candidate to implement the futuristic VLSI circuits. It provides a great scalability, near-zero standby power consumption, etc. In order to design memristor based VLSI circuits and explore their potential, it is crucial to develop an automated design flow. However, such a design flow is still missing so far. This paper proposes an automated design flow, Mosys by reusing parts of existing CMOS VLSI circuit design tools. Mosys provides a circuit design flow from a Verilog programming interface to performance estimation models. In addition, it employs a probabilistic power estimation model instead of one based on exhaustive-searching method. In our experiments, it significantly reduces the running time up to over 3000 times with a marginal error (<1%), as compared to the state-of-the-art. To verify the whole Mosys flow, several integer arithmetic functional units (e.g., add, multiply) are described in Verilog and implemented. In addition, Mosys is compared with the state-of-the-art using the EPFL benchmark suite. The results show that Mosys significantly improves the area (6.29x) and delay (4.68x) on average. • Our proposal can improve the state-of-the-art in the following aspects. • It provides a programming interface to facilitate the development of the VLSI circuits. • It employs a probabilistic power estimation model instead of one based on exhaustive-searching method. It significantly reduces the running time up to over 3000 times with a marginal error (< 1%). • It significantly improves the area (6.29x) and delay (4.68x) on average [ABSTRACT FROM AUTHOR]

• The method to verify the quality of the FM/SC single junction was present. • The effects of potential strength and particle effective mass were compared. A new approach to verify the quality of the magnetic tunnel junction between a ferromagnet and a superconductor single junction (FM/SC) is presented. In this work, we theoretically studied the tunneling conductance spectra of a FM/SC using the scattering method under a free electron approximation model in a two dimensional system. The main area of interest was the physical properties of a junction that was defined by the Dirac delta potential. It was found that the kinks occurring at the energy scale of the ferromagnetic material were suppressed when increasing the strength of the interfacial scattering, but they dominated at the metallic limit of the junction, where the potential strength at the junction was weak. Experimentally, this feature can be used to identify the quality of a ferromagnetic and superconductor junction by considering the shape of those kinks. Furthermore, when the effect of interfacial scattering Z and the conductivity mismatch on the conductance spectra were considered and compared, we found that the conductance spectra of the junction was sensitive to a change in the strength of Z. [ABSTRACT FROM AUTHOR]

• Mo capped pMTJs show high TMR and thermal stability. • Above ∼35 nm H c is size-independent. • The VCMA effect is present even at 20 nm diameters. Co 20 Fe 60 B 20 /MgO/Co 20 Fe 60 B 20 perpendicular magnetic tunnel junctions with Mo seed and capping layers were patterned into sub-100 nm diameter devices. The resulting devices were imaged in plan view by scanning electron microscopy and in cross-section by scanning transmission electron microscopy. The tunnel magnetoresistance was ∼125%. The coercivity dropped off below 35 nm, and the stray field increased with decreasing diameter. The voltage controlled magnetic anisotropy effect was observed for all sizes, though it was convoluted with thermal and stray field effects for the smaller diameters. [ABSTRACT FROM AUTHOR]

We report a study on the influence of microstructure on the magnetic and electronic properties of nanoscale Sr 2- x La x FeMoO 6 materials. The temperature dependence of the saturation magnetization of the samples in the low temperature range follows the spin wave theory which is described by a T 3/2 law. The analysis of the temperature dependence of the conductivity of the sample with x = 0 shows distinct mechanisms of spin-dependent tunneling and spin-independent hoping channels. Up on La substitution, additional metallic-type conduction paths appear which reduces the resistivity of the samples and also changes its temperature dependence behavior. Spin polarization as a function of temperature was obtained via fitting the MR curves recorded at different temperatures using the spin-dependent elastic tunneling model with correction for the spin-independent conductance. At a temperature 5 K, the spin polarizations of the samples are found to be roughly proportional to the net magnetic moment. Moreover, their values are considerably higher than those derived from theoretical calculations for the double perovskite lattices with the same antisite disorder levels which reveals an inhomogeneous distribution of the antisite defects in the samples. The decay rate of the spin polarization with increasing temperature is faster for the samples with a larger amount of antisite defects. • Sr 2- x La x FeMoO 6 samples (x = 0 – 0.4) were prepared by using sol-gel method and heat treatment in H 2 atmosphere. • Temperature dependence of saturation magnetization follows the Bloch law (∼ T 3/2). • Electrical conduction mechanisms were analyzed. • Spin polarization values were determined based on magnetoresistance data in temperature range 5–300 K. [ABSTRACT FROM AUTHOR]

In this work, we investigated the sensing challenges of spin-transfer torque MRAMs structured with perpendicular magnetic tunnel junctions with a high tunneling magnetoresistance ratio in a low resistance-area product. To overcome the problems of reading this type of memory, we have proposed a voltage sensing amplifier topology and compared its performance to that of the current sensing amplifier in terms of power, speed, and bit error rate performance. We have verified that the proposed sensing scheme offers a substantial improvement in bit-error-rate performance. To enumerate the read operations of the proposed sensing scheme with the proposed cross-coupled capacitive feedback technique on the clamped circuity have successfully been performed a 2.5X reduction in average low power and a 13X increase in average reading speed compared with the previous works due to its device structure and the proposed circuit technique. [ABSTRACT FROM AUTHOR]

We investigated the effect that Ta spacer had on the interfacial microstructures and magnetic properties of MgO/CoFeB/Ta/CoFeB/MgO films. We found that when the Ta spacer thickness was optimized, the double MgO interface led to an enhancement in the perpendicular magnetic anisotropy (PMA) and thermostability. By systematically studying the changes for different structures in the chemical state, we interpreted how elements diffuse and alter the chemical states and properties of the magnetic tunnel junctions (MTJs). We found that increasing the Fe oxide is crucial to the PMA in the films and we attribute the increase in the of Fe oxide content to the oxygen liberated by the reduction of boron oxide. • The magnetic properties and thermal stability of MgO/CoFeB/Ta/CoFeB/MgO films were studied. • Fe oxide was increased through the oxygen liberated by the reduction of boron oxide. • The formation of minor Fe(Co)oxide at the CoFeB/MgO interface enhanced the PMA. [ABSTRACT FROM AUTHOR]

Position of impurities at point defects of a compound have an important role in determine the physical or chemical properties of semiconductor materials. Hence, an accurate and efficient theoretical tool is needed in order to have a deep understanding and logic explanation for the physical phenomenon observed. Therefore, first principles calculation was used to investigate the effect of impurities position at point defects of Au atom in the ZnO semiconductor material on thermoelectric and magnetic performance. In this work, density functional theory based on the generalized-gradient-approximation (GGA) and the Boltzmann transport theory have been used to calculate the structural, electronic, magnetic and thermoelectric properties of Au doped ZnO at different point defect's position (interstitial and substitutional). The obtained results give a hexagonal wurtzite structure with the space group of P 63 mc and the formation energy at the interstitial model indicated 0.2331 eV lower rather than the substitution model. This indicated more stable structure at the interstitial sites with n -type degenerated semiconductor characteristic and behaves as a diamagnetic material with highest electronic thermal conductivity. Whereas, the substitution of Zn by Au produces p -type semiconductor characteristics with the presence of magnetism properties (0.916 μ b of total magnetic moment) and enhance the electrical conductivity properties. The Seebeck coefficient obtained is in excellent accord with the experimental data of Au doped ZnO. The result shows that Au doped ZnO can be used in the thermoelectric power generated in magnetic tunnel junction (MTJ) applications. • Magnetic and thermoelectric properties of Au doped ZnO at different point defects are investigated with DFT. • Substitution model show that Au doped ZnO is ferromagnetic, interstitial show paramagnetic behavior. • Hybridization between p-d states are responsible for electrical transport properties and magnetic properties. [ABSTRACT FROM AUTHOR]

Driven by the trends of emerging technologies in memories, a non-volatile memory (NVM) has been considered as an alternate technology to replace SRAM in an on-chip cache. Spin-transfer torque random access memory (STT-RAM), a new type of NVM technology has low leakage power and huge density of cells. Besides having advantages, the emerging NVM technologies have limited writes and huge error rates. The write endurance and error rates are influenced by the cache replacement algorithm, which ultimately dictates the lifetime of a cache. Hence, it becomes necessary to develop or modify the cache replacement algorithms for improving the lifetime of the STT-RAM caches. The proposed Hybrid-Cache-Replacement (HCR) policy reduces the impact of the replacement algorithm in such a way that its write endurance improves with reduction in error rate. The incoming data are appropriately placed in the existing block, which have minimum error rates and less number of writes. It has been implemented by comparing the incoming bits with the existing bits in a cache set. The simulation results show that the lifespan of the STT-RAM caches improves by 135%, 165% and 27% along with 2%, 2% and 1% performance overhead when compared to the existing methods. • A Non-Volatile Memory (NVM) is an alternate technology to replace SRAM in an on-chip cache. • A new type of NVM technology such as STT-RAM has low leakage power and huge density of cells. But it has limited writes and huge error rates. • The limited writes and error rates can be improved by modifying or developing a cache replacement algorithm. • The proposed Hybrid-Cache-Replacement (HCR) policy\ improves the write endurance by reducing the 0-1 transitions. [ABSTRACT FROM AUTHOR]

Highlights • We study annealing effect on memory states stability in CoFeB/MgO/CoFeB based perpendicular MTJs. • Our study indicates a ferromagnetic coupling between the storage and reference layers. • Enhance pMTJs stability by playing perpendicular magnetic anisotropy and interlayer coupling. Abstract Perpendicular magnetic tunnel junctions (p-MTJs) attract great interest because of their excellent performance in spin-transfer-torque magnetic random access memories (STT-MRAMs). The annealing process is critical to achieve the required structural and magnetic properties, therefore obtaining high perpendicular tunneling magnetoresistance (p-TMR) and lower switching current. In this work, the CoFeB/MgO/CoFeB-based p-TMR stack was prepared and a high p-TMR value of 155.9% was obtained from CIPT. The p-MTJs were patterned with pillar sizes ranging from 50 nm to 1000 nm and were annealed upon different annealing temperatures (T A) of 300 and 340 °C. The resistance at parallel (R P) and antiparallel (R AP) state in p-MTJs was obtained upon the application of a ±30 mT perpendicular magnetic field, where the angle of magnetization between storage and reference layer at memory state, θ P and θ AP , were derived from the P and AP resistance ratios with and without magnetic field. The condition θ P = θ AP of about 63.5° was found in as-deposited samples, indicating a ferromagnetic interlayer coupling between storage and reference layers, where θ P = 0° and θ AP = 180° at T A = 300 °C and 340 °C demonstrate a stable memory state. The stability of the resistance state was modeled by considering the evolution of effective perpendicular magnetic anisotropy (K eff) and interlayer coupling constant (J), showing a method to evaluate the ratio of K eff / J via the memory state resistance characterization, where the K eff / J of about −1.26 was obtained in our as-deposited samples. Our study assesses the effect of T A on the θ P and θ AP and supplies the method to enhance the stability through the optimization of perpendicular magnetic anisotropy and interlayer coupling, so to better control the performance of p-MTJ-based STT-MRAMs. [ABSTRACT FROM AUTHOR]

Highlights • A Ni/Gr/h-BN/Gr/Ni nanostructure was constructed and its spin-dependent transmission properties were simulated. • This device combines the spin filtering of Gr/FM interface and the resonant tunneling of Gr/h-BN/Gr heterostructure. • An effective approach was demonstrated to control spin current based on the bias tunability of the resonance tunneling. • Spin resonance results in a large magnetoresistance and negative differential resistance in the device. Abstract Future development of spintronic devices urgently requires an advanced control method of spin current. Combining graphene with other various characteristic two-dimensional crystals in different ways can produce a new class of functional materials, which offers a unique platform for spintronics. A specific van der Waals heterostructure consisting of graphene and hexagonal boron nitride (h-BN) as the barrier layer in magnetic tunnel junctions (MTJs) is proposed in this paper. This heterostructure device combines the strong spin filtering effect of graphene/ferromagnet interface and the resonant tunneling effect of graphene/h-BN/graphene van der Waals heterostructure. We demonstrate an effective approach to control spin current based on the bias tunability of the spin resonance tunneling transport. Theoretical research unambiguously reveals that spin resonance appears when the electronic spectra of spin electron in two graphene layers are aligned, which results in a large magnetoresistance and negative differential resistance in the device. The efficient bias controllability of spin current, combined with the excellent magnetoresistance behavior, can be the key building blocks in future spin-based magnetic detection and high-frequency logic devices. [ABSTRACT FROM AUTHOR]

Abstract The tunneling rate of a particle between two sites situated in different sublattices of a single-layer graphene sheet which can interact with the conduction electrons has been calculated. The interaction between the impurity sites is decisive in determining the tunneling rate. Furthermore, the rate also depends on the energy of the impurities along with value of the chemical potential of the system. Highlights • The tunneling rate between the two impurity sites in graphene is calculated. • The appropriate channels for tunneling was also identified. • The spin-contribution towards tunneling was demonstrated. [ABSTRACT FROM AUTHOR]

Highlights • This study focuses on the magnetic properties of MTJ based STT-MRAM. • Initial temperature increment in the device influences to the magnetic properties. • Switching energy can be reduced by increase of both initial temperature and angle in free layer. • This study benefits to the technology development of magnetic memory devices in near future. Abstract Spin transfer torque random access memory (STT-RAM) based on magnetic tunnel junction (MTJ) is a popular type of memory because of its non-volatility, small size, and nanosecond access time. The temperature effect on the magnetic properties and the initial angle between the free and pinned layer magnetizations in the MTJ cell are significant for the fast switching process in STT-RAM. In this study, the switching energy was investigated with the temperature effect on the magnetic properties at various initial angles. The results show that the saturation magnetization was decreased by increments of the initial temperature, which also resulted in the reduction of the intrinsic critical current density. Consequently, switching energy can be reduced by the increase of both the initial temperature and the initial angle. Although the initial temperature increment in the MTJ cell is interesting for the fast switching process in STT-RAM, the thermal stability factor greater than 40 and the Curie temperature were both considered for the analysis of the switching energy with magnetic properties, for stabilizing the operation of STT-RAM. [ABSTRACT FROM AUTHOR]

Highlights • New reconfigurable logic concept is proposed by using two-input configuration of magnetic tunnel junction. • NAND and NOR functions are performed in fixed architecture with selection of voltage inputs. • Carry-out function in a full adder is demonstrated through a method for the reconfigurable logic. Abstract We propose a method for reconfigurable logic using a single magnetic tunnel junction (MTJ) as the main computing element in the single-gate architecture. The introduction of the MTJ to reconfigurable computing provides advantages in layout efficiency, power consumption, and the device variation problem. In this study, we present a three-terminal MTJ implemented by two inputs (ampere magnetic field and spin torque-transfer current) acting as a logic element that performs the Boolean logic functions of NAND and NOR with corresponding programmable input values in a fixed architecture. In addition, the reconfigurable functionality is confirmed through demonstration of carry-out computing across the operator built with single-MTJ logic architecture. [ABSTRACT FROM AUTHOR]