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The spin injection efficiency in the Ferromagnetic/Nonmagnetic Semiconductor/Ferromagnetic (FM/NMS/FM) structures was studied under external magnetic and electric fields. It is found that spin injection efficiency can be strongly influenced by magnetic and electric fields. With the increase of these fields, the down-stream spin diffusion length increases and makes the spin injection efficiency increase. Furthermore, the effects of many-body correlations and exchange reduces the value of the diffusion constant that leads to enhance spin injection efficiency. [ABSTRACT FROM AUTHOR]

Achieving highly efficient spin injection has been a challenging problem for a long time in spin logic devices. The chiral-induced spin selectivity (CISS) effect could induce spin polarization of electron transmission by chiral structure, providing a promising solution to resolve the above bottleneck. In this work, the significant CISS effect by self-assembled chiral organic molecules with helical structure was achieved on the copper (Cu) substrate covered with gold (Au) layer. We find that the spin polarization induced by the chiral molecules is more than 80%. Serving as an ultra efficient spin filter, the chiral organic molecules is demonstrated to be an effective way to generate pure spin currents and achieve highly efficient spin injection without ferromagnetic electrodes or external magnetic field. Based on these properties, a CISS based reconfigurable logic device is proposed. Due to the high spin injection efficiency, this CISS based device can realize 6 different logic operations with low energy consumption (1.2 pJ) and high speed (3.6 ns). [ABSTRACT FROM AUTHOR]

First-principles investigations are performed on magnetic tunnel junctions (MTJs) constructed with chromium trihalide CrCl3 as barrier and half metallic ferromagnet (HMF) CrO2 as electrodes using density function theory (DFT) calculations, and the results are compared with CrBr3 and CrI3. On comparing the results obtained after performing the first-principles investigation on CrCl3, CrBr3, and CrI3, it is understood that CrCl3 offers very high tunnel magnetoresistance (TMR) of ~ 100% and spin injection efficiency (η) of ~ 100% for different bias voltages, and spin transport occurs due to tunneling which is evident from the transmission spectrum. Although CrBr3 has TMR greater than 95% and spin injection efficiency (η) of ~ 100%, transmission states are present at the Fermi level, hence, tunneling is not the phenomenon in the case of CrBr3. CrI3 suffers from fluctuations in both TMR and spin injection efficiency (η) over the applied bias voltage range and has more spin-up current and spin-down current in both parallel configuration and anti-parallel configuration. In CrI3, as there are states in transmission spectrum at the Fermi level, the spin transport occurs because of band-to-band hopping instead of tunneling. From the results obtained, CrCl3 is identified as the perfect material to be used as the barrier in MTJs. [ABSTRACT FROM AUTHOR]

Using first-principles spin-polarized density functional theory computations, the effect of functionalization (fluorination and hydrogenation) on spin-polarized transport of gallium nitride (GaN) nanosheet–based magnetic tunnel junction (MTJ) with CrO2 as electrodes is investigated. The results show fluorinated GaN–based structure exhibits better spin filtration and high TMR (maximum ~ 99%), as compared with hydrogenated GaN (maximum TMR ~ 93%)– and pristine GaN (maximum TMR ~ 83%)–based structures. In addition, fluorinated GaN nanosheet exhibits a ferromagnetic behavior with a magnetic movement of 1.0 μb per fluorine atom. The magnetic movements for pristine GaN and hydrogenated GaN sheets are reported to be 0 μb and 0.9 μb per hydrogen atom, respectively. Higher TMR, better spin filtration, and ferromagnetic behavior for fluorinated GaN–based structure open up its possibility as spin filter (injector) in MTJs and other spin-based devices. [ABSTRACT FROM AUTHOR]

In this paper, we propose a performance optimization scheme for all-spin logic device (ASLD); this scheme makes use of asymmetric tunneling layer to overcome the conductivity mismatch problem. Besides, for the material selection of device, this scheme makes advantage of silver as an energy efficient interconnect material to reduce the switching delay. The simulation results indicate that the high spin injection efficiency can be obtained by increasing the thickness of the transmitter-side tunneling layer or decreasing the thickness of the receive-side tunneling layer. Therefore, the structure of asymmetric tunneling layer is expected to be more effective for spin injection. Compared with the traditional interconnect that copper or aluminum is used as a channel material, the time for magnetic moment reversal and the spin current flowing into the output magnet are predicated to be optimized when silver is chosen as the channel material, which can attribute to the fact that the conductivity of silver material is larger, the spin diffusion length is longer, and the spin–orbit interaction is weaker. Meanwhile, when the critical switching current requires for the magnetization reversal is applied, the reliable working length of silver channel is significantly longer than that of copper or aluminum channel. These abovementioned results provide a new method for the performance optimization of ASLD. [ABSTRACT FROM AUTHOR]

Abstract: The electrical spin injection from Fe into an n-doped GaAs channel through Schottky-tunnel-barrier is observed from 1.8K to room temperature. The magnitude of local spin valve signal (ΔR/R 0) decreases as the temperature increases. In each temperature, we calculated the injected polarization (η) considering the spin drift effect induced by the electric field. The interfacial polarizations of 19.3% and 12.6% are acquired for Fe/GaAs junction at T=1.8 and 300K, respectively. The temperature dependence of spin injection efficiency is matched with interface resistance variation. As the temperature increases, Schottky-tunnel-barrier property is diminished so that the spin injection efficiency would be reduced. [Copyright &y& Elsevier]

Abstract: Spin injection across ferromagnet/organic semiconductor system with finite width of the layers was studied theoretically considering spin-dependent conductivity in the organic-semiconductor. It was found that the spin injection efficiency is directly dependent on the difference between the conductivity of the up-spin and down-spin polarons in the spin-injected organic system. Furthermore, the finite width of the structure, interfacial electrochemical-potential and conductivity mismatch have great influence on the spin injection process across ferromagnet/organic semiconductor interface. [Copyright &y& Elsevier]

Almost all spintronic transistors (e.g., spin field-effect transistors, spin bipolar transistors, and spin-enhanced MOSFETs) require high efficiency of spin injection from a ferromagnetic contact into a semiconductor channel for proper operation. In this paper, we calculate the efficiency of spin injection from a realistic nonideal ferromagnetic contact into the semiconductor quantum wire channel of a spintronic transistor, taking into account the presence of an axial magnetic field (caused by either the ferromagnetic contact or external agents) and spin orbit interaction. In our calculations, the temperature is assumed to be low enough that phonon scattering is weak and transport is phase-coherent, although not ballistic because of elastic scattering caused by impurities and defects. We consider a single impurity in the channel and show that the conductance depends strongly on the exact location of this impurity because of quantum mechanical interference effects. This is a nuisance since it exacerbates device variability. The ldquosignrdquo of the impurity potential, i.e., whether it is attractive or repulsive, also influences the channel conductance. Surprisingly, at absolute zero temperature, the spin injection efficiency can reach 100% at certain gate biases, even though the ferromagnetic injector is nonideal. However, this efficiency drops rapidly with increasing temperature. [ABSTRACT FROM PUBLISHER]

• Thermal spin Seebeck effect is observed in VSe 2 monolayer based device. • Temperature dependent giant magnetoresistance is observed in VSe 2 monolayer based device and increases with Δ T. • Higher spin-injection efficiency at lower value of Δ T and T L (left electrode temperature) An applicable use of a linear combination of atomic orbitals (LCAO) based density functional theory (DFT) together with non-equilibrium Green's function (NEGF) is performed for investigating the dependence of temperature on spin-resolved transport characteristics of electron in magnetic Vanadium Diselenide (VSe 2) monolayer. To know the dependence of heat (temperature) on spin Seebeck effect and spin filtration, important factors like transmission spectrum and spin-resolved current are calculated. Approximately 100% spin injection efficiency is attained in the low-temperature gradient. Low temperature (T L) of cold (left) electrode with respect to high temperature (T R) of hot (right) electrode leads to a smaller spin injection efficiency. Giant thermal magnetoresistance around 3.936 × 103% is achieved and this giant thermal magnetoresistance is directly proportional to the difference between the temperature of right and left electrode (Δ T). This resultant thermal magnetoresistance is also dependent on T L. A large value of temperature gradient based magnetoresistance (MR) and magnificent temperature gradient based spin filtration have been achieved for VSe 2 monolayer advocates the useful application of this compound in the area of spin caloritronic. [ABSTRACT FROM AUTHOR]