Spin transfer torque in magnetic semiconductors

Paul Haney (NIST, CNST)

Spin transfer torque is an effect whereby the application of a charge current can change the magnetization direction of a ferromagnet. It is most often studied in metallic ferromagnets in a multilayer geometry. These systems are well understood, and hold the promise for high density magnetic random access memory (MRAM). I am interested in how the spin transfer torque effect is manifest in a slightly different class of materials, namely magnetic semiconductors. Magnetic semiconductors have properties that qualitatively distinguish them from metallic ferromagnets, and which make the conventional theory of spin transfer torque inapplicable. Magnetic semiconductors also offer greater functionality than their metallic counterparts, although they are currently only found at low temperatures. In this talk I will review spin transfer torque in metallic systems, and discuss the results of our theoretical studies of spin transfer torque in magnetic semiconductors. We have found that the origin and basic properties of spin transfer in magnetic semiconductors are qualitatively different from conventional (i.e. metallic) materials.

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