Electrically driven magnetization of diluted magnetic semiconductors actuated by theOverhauser effect

Abstract

It is well known that the Curie temperature, and hence themagnetization, in diluted magnetic semiconductors (DMS) likeGa1 − xMnxAs can be controlled by changing the equilibrium density of holes in the material. Here, wepropose that even with a constant hole density, large changes in the magnetization can beobtained with a relatively small imbalance in the quasi-Fermi levels for up-spinand down-spin electrons. We show, by coupling the mean field theory of dilutedmagnetic semiconductor ferromagnetism with master equations governing the Mnspin-dynamics, that a mere splitting of the up-spin and down-spin quasi-Fermi levels by0.1 meV will produce the effect of an external magnetic field as large as1 T as long as the alternative relaxation paths for Mn spins (i.e. spin–lattice relaxation) canbe neglected. The physics is similar to the classic Overhauser effect, also called the dynamicnuclear polarization, with the Mn impurities playing the role of the nucleus. Wepropose that a lateral spin-valve structure in an anti-parallel configuration with aDMS as the channel can be used to demonstrate this effect, as quasi-Fermi levelsplitting of such magnitude, inside the channel of similar systems, has already beenexperimentally demonstrated to produce polarization of paramagnetic impurityspins.