Abstract
In order to elucidate the origin of ferromagnetism in (Zn,Cr)Te, combined analyses of magnetization measurements and structural and chemical characterizations were performed on a series of epitaxial films grown by molecular beam epitaxy. The magnetic properties of (Zn,Cr)Te films were altered significantly by co-doping charge impurities or by changing Zn and Te flux supplies during epitaxy. The nano-scale probing of the constituent elements using energy-dispersive X-ray spectroscopy (EDS) revealed that the Cr distribution in the crystal was clearly correlated with the ferromagnetic properties and the origin of high-temperature ferromagnetism was the formation of nano-scale Cr-rich regions in inhomogeneous Cr distributions. As an origin of the variation of the uniformity of Cr distribution, it is proposed that the aggregation energy of Cr ions is modified by the deviation of the Cr charge state which is manipulated by the co-doping or the deviation from stoichiometry.