Berlin 2008 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 19: Symposium Spin Effects in Semiconductors of Reduced Dimensionality

HL 19.1: Invited Talk

Tuesday, February 26, 2008, 10:30–11:00, ER 270

Novel devices using local control of magnetic anisotropies in (Ga,Mn)As. — •Charles Gould, Jan Wenisch, Silvia Hümpfner, Katrin Pappert, Manuel Schmidt, Christian Kumpf, Karl Brunner, Georg Schmidt, and Laurens W. Molenkamp — Physikalisches Institut, Universitat Wuerzburg, Am Hubland, D-97074 Wuerzburg, Germany

(Ga,Mn)As has long been the prototypical ferromagnetic semiconductor for investigations into spintronics devices, in large part because of its rich magnetic anisotropies. Until recently, all devices simply inherited their magnetic anisotropy from the bulk parent layer from which they were formed. To produce more sophisticated devices, a method of local anisotropy control of device elements is needed. Moreover, using shape anisotropy, which is effective in metals, will not work because of the relatively low magnetization and the strong crystalline anisotropies in magnetic semiconductors.

In this talk, I will present our discovery of a novel method for local anisotropy control. The method is based on using nano-lithography to pattern the (Ga,Mn)As in such a way as to cause anisotropic strain relaxation. The strong spin-orbit coupling in the material, which links the magnetic properties to the crystal structure, then leads to a new anisotropy term which can be engineered to completely control the local anisotropy of device elements.

To demonstrate the usefulness of this method, I will present a non-volatile memory element consisting of two nanobars, orthogonal to each other, and each with a uniaxial anisotropy along its primary axis.