Domain-wall controlled (Ga,Mn)As nanostructures for spintronic applications

Valence-band structure and magnetic properties, especially magnetic anisotropies, in the (Ga,Mn)As diluted ferromagnetic semiconductor are shortly discussed. Next, magneto-resistive, cross-like nanostructures fabricated by electron-beam lithography patterning and chemical etching from thin (Ga,Mn)As epitaxial layers are described. The nanostructures, composed of two perpendicular nanostripes crossing in the middle of their length, represent four-terminal devices, in which an electric current can be driven through any of the two nanostripes. In these devices, which make use of the patterning-induced magnetic anisotropy, a novel magneto-resistive memory effect related to a rearrangement of magnetic domain walls in the central part of the device, has been demonstrated. The effect consists in that the zero-field resistance of a nanostripe depends on the direction of previously applied magnetic field. The nanostructures can thus work as two-state devices providing basic elements of nonvolatile memory cells.