Comparison of the magnetic properties of GeMn thin films through Mn L-edge x-ray absorption

摘要

X-ray absorption spectroscopy of epitaxial GeMn thin films reveals an experimentally indistinguishable electronic configuration of Mn atoms incorporated in Ge_(1-x)Mn_x nanoclusters and in precipitates of the intermetallic compound Mn_5Ge_3, respectively. However, the average magnetic response of thin films containing Ge_(1-x)Mn_x nanoclusters is lower than the response of films containing Mn_5Ge_3 precipitates. This reduced magnetic response of Ge_(1-x)Mn_x nanoclusters is explained in terms of a fraction of Mn atoms being magnetically inactive due to antiferromagnetic coupling or the presence of structural disorder. A determination of the role of magnetically inactive Mn atoms in the self-assembly of the thermodynamically metastable Ge_(1-x)Mn_x nanoclusters seems to be an essential ingredient for an enhanced control of this promising high Curie temperature magnetic semiconductor.