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We have performed conductivity measurements on a Si-MOSFET sample with a slot in the upper gate, allowing for different electron densities n1 and n2 across the slot. Dynamic longitudinal resistance was measured by a standard lock-in technique, while maintaining a large dc current through the source-drain channel. We find that in a parallel magnetic field, the resistance of the sample R(Idc) is asymmetric with respect to the direction of the dc current. The asymmetry becomes stronger with an increase of either the magnetic field or the difference between n1 and n2. These observations are interpreted in terms of the effective spin injection: the degree of spin polarization is different in the two parts of the sample, implying different magnitudes of spin current away from the slot. The carriers thus leave the excess spin (of the appropriate sign) in the region around the slot, leading to spin accumulation (or depletion) and to the spin-drift-diffusion phenomena. Due to the positive magnetoresistance of the two-dimensional electron gas, this change in a local magnetization affects the resistivity near the slot and the measured net resistance, giving rise to an asymmetric contribution. We further observe that the value of R(Idc) saturates at large Idc; we suggest that this is due to electron tunneling from the two-dimensional n-type layer into the p-type silicon (or into another "spin reservoir") at the slot. [ABSTRACT FROM AUTHOR]

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]

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]

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]

Abstract: Due to the competition between spatial and magnetic confinement, the density of states (DOS) of a quasi-two-dimensional system deviates from the ideal step-like form both quantitatively and qualitatively. We study how this affects the spin-subband populations and the spin polarization as functions of the temperature, T, and the in-plane magnetic field, B, for narrow to wide dilute-magnetic-semiconductor quantum wells (QWs). We focus on the QW width, the magnitude of the spin–spin exchange interaction, and the sheet carrier concentration dependence. We look for ranges where the system is completely spin polarized. Increasing T, the carrier spin splitting, , decreases, while on increasing B, increases. Moreover, due to the DOS modification, all energetically higher subbands become gradually depopulated. [Copyright &y& Elsevier]