Lattice distortion of MnAs nanocrystals embedded in GaAs:: Effect on the magnetic properties -: art. no. 161903

The x-ray coherent scattering in nanosized MnAs crystallites embedded in a GaAs matrix has been detected. The room-temperature interatomic distances along three orthogonal directions of the crystallites are determined. The MnAs nanocrystals are found to exhibit an anisotropically distorted hexagonal structure as compared to unstrained bulk MnAs. Despite the crystallite lattice distortion, the granular GaAs:MnAs material exhibits robust ferromagnetism, with enhanced transition temperature. The observed magnetic behavior is consistently explained by a localized double-exchange model of MnAs ferromagnetism, where magnetic order appears for large enough Mn-As-Mn distances, i.e., for weak enough p-d hybridization. (c) 2005 American Institute of Physics.