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In this paper, we theoretically investigate how to control spin filtering via a δ -doping for electrons in a magnetically and electrically modulated semiconductor nanostructure (MEMSN), which can be realized by patterning a ferromagnetic (FM) stripe and a Schottky-metal (SM) stripe on top and bottom of GaAs/AlxGa 1 − x As heterostructure in experiments, respectively. A considerable spin filtering effect still exists because of spin–orbit coupling (SOC), even if a δ -doping is included. Moreover, spin polarization ratio can be manipulated by δ -doping, which may lead to a structurally-controllable electron-spin filter for semiconductor spintronics. [ABSTRACT FROM AUTHOR]

We theoretically explore how to control electron-spin polarization in layered semiconductor nanostructure (LSN) by a δ -potential realized by atomic-layer doping. Due to Rashba spin-orbit coupling, a considerable spin polarization still remains even through a δ -potential is embedded in the LSN. Spin polarization ratio can be controlled by altering weight or position of δ -potential. Based on such an LSN, a structurally-tunable electron-spin filter may be obtained for spintronics device applications. [ABSTRACT FROM AUTHOR]

We report first-principles investigation on structural, electronic and magnetic properties of 3d transition metal element-doped rock-salt calcium selenide Ca 1 − x TMxSe (TM = V, Cr and Mn) at concentrations x = 0.0625, 0.125 and 0.25. We performed the calculations in the framework of the density functional theory (DFT) using the full-potential linearized augmented plane waves plus local orbitals (FP-LAPW+lo) method within the Wu–Cohen generalized gradient approximation (WC-GGA) for the structural optimization and the Tran–Blaha modified Becke–Johnson (TBmBJ) potential for the electronic and the magnetic properties. The computed spin-polarized band structures and densities of states show that Ca 1 − x CrxSe compounds at all studied concentrations are half-metallic ferromagnets with a complete spin polarization of 100% at Fermi-level while the Ca 1 − x VxSe and Ca 1 − x MnxSe are ferromagnetic semiconductors. The total magnetic moments for Ca 1 − x VxSe, Ca 1 − x CrxSe, and Ca 1 − x MnxSe show the integer values of 3 μ B , 4 μ B , and 5 μ B , respectively, with a major contribution of transition metal elements (TM) in the total magnetization. Also, we reported the calculated exchange constants N 0 α and N 0 β and the band edge spin splitting of the valence (Δ E v ) and conduction (Δ E c ) bands. The ferromagnetism of these compounds is due to the super-exchange and the double-exchange mechanisms in addition to the strong p–d exchange interaction. Therefore, the predicted results indicate that the diluted Ca 1 − x TMxSe (TM = V, Cr, Mn) compounds are suitable candidates for a possible application in the field of spintronic technology. [ABSTRACT FROM AUTHOR]

The aim purpose of this study is to investigate the structural, elastic, magnetic, electronic properties and half-metallic stability under pressure of ScNiCrZ (Z = Al , Ga and In) quaternary Heusler alloys using full-potential linear muffin-tin orbital (FP-LMTO) method within the gradient generalized approximation (GGA) for exchange, and correlation potential. In order to evaluate the stability of our compounds, the formation energy, and elastic constants have been evaluated. The results showed that our compounds have ferromagnetic ground states and are energetically more stable in type- γ configuration. True half-metallic ferromagnetic behavior with 100% spin polarization at Fermi level E F with high Curie temperature T c , and very interesting bandgap in the minority spin are obtained for the three alloys. The calculated total magnetic moment M T for all three alloys is consistent with Slater − Pauling rule. The half-metallicity is maintained over a wide range of lattice constants making these alloys promising for spintronic, and magneto-electronics applications. [ABSTRACT FROM AUTHOR]

We theoretically investigate dwell time for electrons in a magnetic nanostructure with a δ -doping, which is formed on InAs / Al x In 1 − x As heterostructure by depositing a ferromagnetic (FM) stripe. We find that dwell time depends strongly on electron-spins owing to Zeeman coupling and broken symmetry. We also demonstrate that spin-polarized dwell time can be manipulated by δ -doping. Thus, electron spins can be separated in time dimension and such a magnetic nanostructure can be employed as a structurally-controllable temporal spin splitter for spintronics device applications. [ABSTRACT FROM AUTHOR]

Half-metals and spin gapless semiconductors (SGSs), which exhibit 100% spin polarization at the Fermi level, are considered important candidates for spintronics. Using first-principles calculations, we have investigated the effects of uniform strain and tetragonal distortion on the half-metallicity and spin gapless feature of inverse Heusler Ti2 YSi ( Y = Fe and Co) alloys. Results show that for uniform strains, the half-metallicity occurs in the ranges of lattice parameters from 5.938 Å to 6.535 Å for Ti2FeSi and from 5.924 Å to 6.840 Å for Ti2CoSi. Tetragonal distortions over the ranges of −2.0% to +2.5% and −2.6% to +4.1% could destroy the half-metallicity for Ti2FeSi and Ti2CoSi, respectively. On the other hand, Ti2CoSi is an SGS at lattice constants of 5.968-6.023 Å. An interesting finding is that Ti2CoSi reproduces the SGS character with increasing the lattice parameters to 6.784-6.840 Å. Small tetragonal distortions with ±0.2% will destroy the SGS character of Ti2CoSi. [ABSTRACT FROM AUTHOR]

The spin polarization of polarons in quasi-1D organic materials has been investigated by using the extended Su-Schrieffer-Heeger (SSH) model with spin-orbit coupling. Results show that the polaron is partly spin polarized, and that the electron-electron interaction and spin-orbit coupling compete with each other during the formation of spin polarization. The dependence of spin polarization on electron-phonon coupling is also revealed. Our results demonstrate that spin polarization is well correlated with polaron localization, thus providing useful guidance for exploring magnetic effects in organic materials. [ABSTRACT FROM AUTHOR]

Spin-polarization can be formed by the two components of soliton (electromagnetic wave) within the metallic waveguide. Under the resonant condition, the random transverse electric and magnetic fields of the solitons corresponding to the left-hand and right hand photons can be generated. Whenever a photon is absorbed by an object, an angular momentum of either +ℏ or -ℏ is imparted to the object, in which two possible spin states known as optoelectronic spins are exhibited. Furthermore, the array of optoelectronic spins, i.e., many particles can be generated and controlled by using the modified add-drop filter, in which the broad spectrum soliton can be generated and used to form large scale spin transport applications. [ABSTRACT FROM AUTHOR]

Within the Luttinger Hamiltonian, electric-field-induced resonant spin polarization of a two-dimensional hole gas in a perpendicular magnetic field was studied. The spin polarization arising from splitting between the light and the heavy hole bands shows a resonant peak at a certain magnetic field. Especially, the competition between the Luttinger term and the structural inversion asymmetry leads to a rich resonant peaks structure, and the required magnetic field for the resonance may be effectively reduced by enlarging the effective width of the quantum well. Furthermore, the Zeeman splitting tends to move the resonant spin polarization to a relative high magnetic field and destroy these rich resonant spin phenomena. Finally, both the height and the weight of the resonant peak increase as the temperature decreases. It is believed that such resonant spin phenomena may be verified in the sample of a two-dimensional hole gas, and it may provide an efficient way to control spin polarization by an external electric field. [ABSTRACT FROM AUTHOR]

Recently, an electron-spin filter was proposed by depositing a nanosized ferromagnetic metal stripe and a Schottky normal metal stripe on the top of the semiconductor heterostructure [F. Zhai, H. Q. Xu and Y. Guo, Phys. Rev. B70 (2004) 085308]. This device has a considerable electron-spin polarization and potential application in spintronics. Here we apply a bias to this device and theoretically demonstrate how to manipulate its electron-spin polarization. By numerical simulations, we found that not only the amplitude of the electron-spin polarization but also its sign varies with the bias, giving rise to a bias-tunable spin filter device. [ABSTRACT FROM AUTHOR]

We revisit the properties of spin transport through a semiconductor 2DEG system subjected to the modulation of both a ferromagnetic metal (FM) stripe on top and the Rashba and Dresselhaus spin-orbit interactions (SOIs). The FM stripe has a magnetization along the transporting direction and generates an inhomogeneous magnetic field in the 2DEG plane which is taken as a double-δ shape. It is found that the spin polarization of this system generated from a spin-unpolarized injection can be remarkable only within a low Fermi energy region and is not more than 30% for the parameters available in current experiments. In this energy region, both the magnitude and the orientation of the spin polarization can be tuned by the Rashba strength, the Dresselhaus strength, and the magnetic field strength. The magnetization reversal of the FM stripe cannot result in a change of the conductance, but can rotate the orientation of the spin polarization. The results are in contrast to those in [ J. Phys.: Condens. Matter15 (2003) L31] where a pure spin state for incident electrons is artificially assumed. [ABSTRACT FROM AUTHOR]

We present a GaAs/AlGaAs-based quantum well device capable of achieving an appreciable spin polarization coupled with high electron transmission. Our numerical results indicate that the device is able to achieve a high spin polarization without the need for less commonly used materials with high g-factors required by previously proposed semiconductor-based systems. The electron transmission and spin polarization amplitude of our structure is found to be robust to the length of the parabolic well, which could ease the fabrication of such structures in practical applications. [ABSTRACT FROM AUTHOR]

The spin-galvanic effect and the inverse effect, which yeilds current induced spin polarization, in low dimensional semiconductor structures are reviewed. Both effect are caused by asymmetric spin relaxation in systems with lifted spin degeneracy due to k-linear terms in the Hamiltonian. [ABSTRACT FROM AUTHOR]

The spin-dependent transport of electrons in realistic ferromagnetic/semiconductor hybrid nanosystems was investigated theoretically. This kind of nanosystem can be experimentally realized by depositing a magnetized ferromagnetic strip with arbitrary magnetization direction on the surface of a semiconductor heterostructure. It is revealed that a large spin-polarized current can be achieved in such a device. It is also shown that the spin polarity of the electron transport can be switched by adjusting the structural parameters and location of the ferromagntic strip in the system. These interesting properties may provide an alternative scheme to spin-polarized electrons into semiconductors, and such a nanosystem may be used as a spin filter. [ABSTRACT FROM AUTHOR]

In a biased two-dimensional electron gas, the presence of spin-orbit coupling of both the Rashba and Dresselhaus type leads to a Hall conductivity of charge carriers in the absence of an external magnetic field. We study the dynamical charge-Hall effect, the field-induced spin accumulation, and the magnetoelectric effect for a system with short-range elastic impurity scattering by analytically solving the kinetic equations for the spin-density matrix in the linear response regime. By tuning the strength of the Rashba and Dresselhaus spin-orbit coupling as well as the frequency and direction of the applied electric field, eigenmodes of the spin-coupled system are identified. [ABSTRACT FROM AUTHOR]

The spin-dependent electron transport in a two-dimensional electron gas (2DEG) modulated by a stripe of magnetized ferromagnetic metal under an applied voltage was investigated theoretically. It is revealed that highly spin-polarized current can be achieved in this kind of nanosystems. It is also shown that the spin polarity of the electron transport can be switched by adjusting the applied voltage to the stripe in the device. These interesting properties may provide an alternative scheme to spin polarize electrons into semiconductors, and this device may be used as a voltage-tunable spin filter. [ABSTRACT FROM AUTHOR]

The intrinsic spin Hall effect has been attracting increasing theoretical and experimental interest since its discovery about two years ago. In this article, we review the main achievements in the theoretical aspect of both dissipative and nondissipative spin Hall effects in mesoscopic systems. The Landauer–Büttiker formula and Green's function approach based numerical method for the spin Hall effect is also introduced. [ABSTRACT FROM AUTHOR]

We theoretically investigate the spin-dependent transport properties of electrons in realistic magnetic-electric barrier nanostructures, which are produced by the deposition, on top of a heterostructure, of a metallic ferromagnetic stripe with an applied voltage. The degree of the electron-spin polarization is found to be closely associated with this voltage, although the use of applied voltage itself induces no spin polarization effect. As a positive voltage is applied to the stripe the electron-spin polarization shifts towards the low-energy region and increases; it shifts towards the high-energy direction and reduces for a negative applied voltage. These results shown in this work imply that the degree of electron-spin polarization can be tuned by means of an applied voltage on the stripes of system, which may result in a practical voltage-controlled spin filter. [ABSTRACT FROM AUTHOR]

We study the magnetization and the magnetic phases of II-VI-based n-doped nonmagnetic- semiconductor (NMS) / narrow to wide dilute-magnetic-semiconductor (DMS) / n-doped NMS quantum wells under in-plane magnetic field. The parallel magnetic field is used as a tool, in order to achieve non-step-like density of states in these -appropriate for conduction-band spintronics- structures. [ABSTRACT FROM AUTHOR]