Abstract
The intrinsic ferromagnetism (FM) in phase-change (PC) magnetic materials was studied by first-principle calculations and experiments. The doped Fe or other transition metals tend to substitute at the Sb site of Ge2Sb2Te5. An asymmetric coupling, between p(x) and p(y) rather than p(z) states of Te and d states of Fe, creates magnetic moments and holes in the p band. The findings reveal a strong dependence of FM interaction on Fe-Fe pair distances and crystallographic orientation. A design principle with three criteria is proposed for exploring new PC magnetic materials.