  We obtain control of magnetic anisotropy in epitaxial (Ga,Mn)As by
anisotropic strain relaxation in patterned structures. The strain in the
structures is characterized using sophisticated X-ray techniques. The magnetic
anisotropy before patterning of the layer, which shows biaxial easy axes along
[100] and [010], is replaced by a hard axis in the direction of large elastic
strain relaxation and a uniaxial easy axis in the direction where pseudomorphic
conditions are retained. This strong anisotropy can not be explained by shape
anisotropy and is attributed solely to lattice strain relaxation. Upon
increasing the uniaxial strain anisotropy in the (Ga,Mn)As stripes, we also
observe an increase in magnetic anisotropy.
