Magnetization of free standing GaMnAs

We compared the magnetization curves between as-grown and free standing GaMnAs samples, which were obtained from the same epitaxially grown wafer, to study the influence of epitaxial strain on their ferromagnetic properties. We found that the magnetization and coercive field for the free standing sample have significantly increased about twice as large as those of the as-grown GaMnAs. In addition, the uniaxial ferromagnetic anisotropies, which would not be expected on the basis of crystal symmetry, are remarkably different between the two samples. These results undoubtedly demonstrate that the magnetic properties are strongly influenced by the epitaxially induced strain.