Distorted and undistorted atomic sites in a ferromagnetic semiconductor Ge_0.6Mn_0.4Te film determined by X-ray fluorescence holography

Local atomic structures around Ge and Mn atoms in a ferromagnetic semiconductor Ge_0.6Mn_0.4Te thin film were investigated by performing Ge and Mn Kα X-ray fluorescence holographic experiments. The obtained three-dimensional atomic images revealed that the local structure around Mn formed a rock salt lattice, whereas the lattice around Ge was strongly distorted, which is reflected by a rhombohedral structure of GeTe. The undistorted rock salt environment around the Mn atoms is considered to be a key factor allowing for this alloy to exhibit high-temperature ferromagnetism.