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X-ray absorption spectroscopy of epitaxial GeMn thin films reveals an experimentally indistinguishable electronic configuration of Mn atoms incorporated in Ge1-xMnx nanoclusters and in precipitates of the intermetallic compound Mn5Ge3, respectively. However, the average magnetic response of thin films containing Ge1-xMnx nanoclusters is lower than the response of films containing Mn5Ge3 precipitates. This reduced magnetic response of Ge1-xMnx 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 Ge1-xMnx nanoclusters seems to be an essential ingredient for an enhanced control of this promising high Curie temperature magnetic semiconductor. [ABSTRACT FROM AUTHOR]

Under defined growth conditions ferromagnetic hexagonal Mn5Ge3 precipitates are formed in cubic Ge1-xMnx epilayers. To study the topotaxial relationship of these nanomagnets we perform x-ray diffraction experiments in coplanar as well as in grazing incidence geometries at synchrotron sources. Additionally, to the well defined topotaxial relation derived for buried nanomagnets deep within the Ge layer, we found an additional class of Mn5Ge3 precipitates very close to the surface, with larger inclusion diameter and several different crystallographic orientations with respect to the buried ones. [ABSTRACT FROM AUTHOR]