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Origin of ferromagnetism and the design principle in phase-change magnetic materialsD. Ding, K. Bai, W. D. Song, L. P. Shi, R. Zhao, R. Ji, M. Sullivan, and P. WuData Storage Institute, Agency for Science, Technology and Research (A*STAR), DSI Building 5, Engineering Drive 1, Singapore 117608 and Institute of High Performance Computing, Agency for Science, Technology and Research (A*STAR), Fusionopolis, 1 Fusionopolis Way, #16-16 Connexis, Singapore 138632 Received 31 October 2011; published 9 December 2011 Phys. Rev. B, 2011, 84 214416. 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 px and py rather than pz 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. | |||||||