TY - CHAP A1 - Opel, Matthias A1 - Nielsen, Karl-Wilhelm A1 - Bauer, Sebastian A1 - Goennenwein, Sebastian T. B. A1 - Gross, Rudolf A1 - Cezar, Julio C. A1 - Schmeißer, Dieter A1 - Simon, Jürgen A1 - Mader, Werner T1 - Ferromagnetism and magnetic clusters in cobalt-doped ZnO T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 43 N2 - Ferromagnetic semiconductors (FMS) - i.e. semiconductors exhibiting long-range magnetic ordering - are intriguing materials. However, in spite of intensive research in the last decade, the existence of homogeneous FMS with a Curie temperature around or above room temperature still is controversial. A particularly tedious issue are local sample inhomogeneities or magnetic clusters, which can yield strong magnetic signals resembling the behaviour expected for a homogeneous FMS. Using pulsed laser deposition, we have grown cobalt-doped ZnO films on single crystalline ZnO substrates. Combining x-ray magnetic circular dichroism, DC magnetometry, and AC susceptibility measurements with a detailed structural analysis by high resolution x-ray diffraction, transmission electron microscopy, and electron-spectroscopic imaging, we can unambigously trace the characteristic, ferromagnetic-like behaviour of our ZnO:Co samples at room-temperature to nanometer-sized superparamagnetic metallic cobalt precipitates. Y1 - 2008 UR - http://www.dpg-verhandlungen.de/year/2008/conference/berlin/part/ma/session/3/contribution/6 SN - 0420-0195 SP - S. 430 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER -