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Electron spin polarization properties of the Datta-Das spin field effect transistors are studied by taking into account the coexistence of the Rashba and Dresselhaus effects and an in-plane magnetic field. The transistor is connected to ferromagnetic leads with unparallel polarization. Transmission coefficients can be calculated and thus the Landauer-Büttiker conductance are obtained. Numerical results for the spin polarization of the conductance were discussed in detail. [ABSTRACT FROM AUTHOR]

The spin-dependent electron transport is theoretically investigated in a two-dimensional electron gas, which is periodically modulated by ferromagnetic and Schottky metal (SM) stripes. We find that the spin-dependent transmission and conductance as well as polarization strongly depend on the number of periods. We also find that the transmission and the polarization of transmitted beams periodically change with increasing the width of the SM stripe. [ABSTRACT FROM AUTHOR]

Abstract: Spin injection in an organic semiconductor system under an external electric-field was studied theoretically by considering spin-dependent conductivity. The effect of the spin-dependent electrical-conductivity on the spin-injection efficiency is self-consistently derived. It is found that the spin-injection efficiency depends evidently on the spin-dependent electrical-conductivity. When the spin-injection efficiency increases 20%, the spin-dependent electrical-conductivity increases nearly four orders of magnitude at T = 10 K. With the increase of external electric-field, the spin-dependent electrical-conductivity increases sharply and makes the spin-injection efficiency increase, too. When the external electric-field varies from 1 to 10 mv/μm, the spin-injection efficiency increases almost 10% at room temperature. It seems to be significant to consider the spin-dependent electrical-conductivity under the external electric-field in spin-injected organic system. [ABSTRACT FROM AUTHOR]

Abstract: The electrical properties and magnetoresistance (MR) of CrO2/Fe3O4 composites with opposite spin polarization have been investigated as a function of CrO2 content. Experimental results indicate that the conductivity exhibits an abrupt increase when CrO2 volume fraction ϕ is close to 0.15, where a percolation behavior happens. Magnetoresistance measurement shows a minimum value in the vicinity of percolation threshold at a temperature of 77 K, while this phenomenon cannot be observed at 150 K. Due to spin-dependent tunneling through grain boundary, the reduction in MR at 77 K mainly results from the opposite sign of spin polarizations in the binary half-metal granular CrO2/Fe3O4 composite. [Copyright &y& Elsevier]

Abstract: Using the transfer matrix method, the transmission probability, the spin polarization and the conductance of the ballistic electron are studied in detail in a nanostructure with the periodic applied bias and magnetic barriers. We find that these observable quantities sensitively depend on the number of the periodic magnetic–electric barriers. With the number of the periods increasing, the resonance peaks shift towards right and the number of the resonance peaks is increasing as well as the spin polarization being enhanced. These interesting properties may be helpful for making the bias-tunable spin filter. [Copyright &y& Elsevier]