Structural and magnetic properties of Mn5Ge3 nanoclusters dispersed in MnxGe1−x/Ge(0 0 1)2 × 1 diluted magnetic semiconductors
Résumé
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 × 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 ≈ 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.