Spin switch and spin amplifier: magnetic bipolar transistor in the saturation regime

It is shown that magnetic bipolar transistors (MBT) can amplify currents even in the saturation regime, in which both the emitter-base and collector-base junctions are forward biased. The collector current and the current gain can change sign as they depend on the relative orientation of the equilibrium spin in the base and on the nonequilibrium spin in the emitter and collector. The predicted phenomena should be useful for electrical detection of nonequilibrium spins in semiconductors, as well as for magnetic control of current amplification and for current switching.Comment: 5 pages, 4 figures; paper to a presentation at XXXIII International School on the Physics of Semiconductor Compounds Jaszowiec 200

Computation of the Nonlinear Magnetic Response of a Three Dimensional Anisotropic Superconductor

Many problems in computational magnetics involve computation of fields which decay within a skin depth $\delta$, much smaller than the sample size $d$. We discuss here a novel perturbation method which exploits the smallness of $\epsilon \equiv \delta / d$ and the asymptotic behavior of the solution in the exterior and interior of a sample. To illustrate this procedure we consider the computation of the magnetic dipole and quadrupole moments of an anisotropic, unconventional, three dimensional superconductor. The method significantly reduces the required numerical work and can be implemented in different numerical algorithms.Comment: Three pages. To appear in Journal of Applied Physics (MMM-Intermag issue

A proposal for a spin-polarized solar battery

A solar cell illuminated by circularly-polarized light generates charge and spin currents. We show that the spin polarization of the current significantly exceeds the spin polarization of the carrier density for the majority carriers. Based on this principle we propose a semiconductor spin-polarized solar battery and substantiate our proposal using analytical arguments and numerical modeling.Comment: 4 pages, 3 figure