Ferromagnetic epilayers vs. antiferromagnetic clusters

¹ CEA-CNRS group “Nanophysique et Semi-conducteurs” Laboratoire de Spectrométrie Physique, Université Joseph Fourier-Grenoble I, and DRFMC-SP2M, CEA Grenoble - 38054 Grenoble, France
² Laboratoire de Magnétisme Louis Néel, CNRS - BP166, 38042 Grenoble, France
³ Laboratoire de Cristallographie, CNRS - 38042 Grenoble Cedex-09, France

Received: 14 July 2003
Accepted: 8 December 2003

Abstract

-doped wurtzite epilayers have been grown by nitrogen plasma-assisted molecular-beam epitaxy. Correlated SIMS, structural and magnetic measurements show that the incorporation of strongly depends on the conditions of the growth. Hysteresis loops which persist at high temperature do not appear to be correlated to the presence of . Samples with up to 2% are purely substitutional _x epilayers, and exhibit paramagnetic properties. At higher contents, precipitates are formed which are identified as clusters by X-ray diffraction and absorption: this induces a decrease of the paramagnetic magnetisation. Samples co-doped with enough exhibit a new feature: a ferromagnetic component is observed up to , which cannot be related to superparamagnetism of unresolved magnetic precipitates.