Structure of Ferromagnetic CrAs Epilayers Grown on GaAs(001).
Résumé
Magnetic and structural properties of CrAs epilayers grown on GaAs(001) by molecular beam epitaxy have been studied. CrAs epilayers are orthorhombic for all thicknesses investigated but show a structural transition from a metastable phase for very thin films, to the usual bulk MnP-type orthorhombic phase at higher thicknesses. At intermediate thicknesses, there is a predominance of the new phase, although a contribution from the usual CrAs bulk phase remains clearly present. These results strongly suggest that the ferromagnetic signal measured at room temperature comes from the new metastable orthorhombic structure with an expanded b-axis induced by the substrate strain.
Mots clés
chromium compounds
magnetic epitaxial layers
molecular beam epitaxial growth
magnetisation
lattice constants
ferromagnetic materials
spin polarised transport
reflection high energy electron diffraction
X-ray photoelectron spectra
transmission electron microscopy
X-ray diffraction
interface magnetism