Structural and magnetic properties of Mn5Ge3 nanoclusters dispersed in MnxGe1-x/Ge(001)2 x 1 diluted magnetic semiconductors

We investigated the structural and magnetic properties of MnxGe1-x, with 0.02 <= x <= 0.1. The MnxGe1-x samples were grown on Ge(0 0 1)2 x 1 by molecular beam epitaxy, at a substrate temperature of 520 K. The samples were characterized in situ by reflection high-energy electron diffraction and ex situ by high-resolution transmission electron microscopy, energy dispersive X-ray reflectivity and magneto-optical Kerr effect. From microscopy images we evidenced on all samples the presence of Mn5Ge3 nanocrystallites in addition to the MnxGe1-x diluted magnetic semiconductor with an estimated Mn concentration x approximate to 1.5%. The size and the density of the Mn5Ge3 precipitates were found to increase with increasing the Mn concentration x. Magnetic analysis showed ferromagnetism with a Curie temperature of 280 K for all samples. (C) 2007 Elsevier B.V. All rights reserved.