Mapping the magnetic anisotropy in (Ga,Mn)As nanostructures

Anisotropic strain relaxation in Ga,Mn As nanostructures was studied combining time-resolved Kerr microscopy and ferromagnetic resonance techniques. Local resonance measurements on individual narrow stripes patterned along various crystallographic directions reveal that the easy axis of the magnetization can be forced perpendicular to the strain relaxation direction. Spatially resolved measurements on disk-shaped and rectangular Ga,Mn As structures allow us to directly visualize these local changes in the magnetic anisotropy. We show that the strain-induced edge anisotropy allows for an effective control of the coercive field in stripe structures.