报告题目：Ferromagnetism in non-magnetic materials-roles of defects

报 告 人：Yuanping Feng，National University of Singapore

报告时间：2014年11月27日16:00

报告地点：理科楼郑裕彤大讲堂

报告摘要：Ferromagnetism in non-magnetic materials has attracted much attention. Many studies have been carried out to identify the origin of the unexpected ferromagnetism, and to explore potential applications of such materials. Following successful prediction of room temperature ferromagnetism in III-V and II-VI semiconductors doped with 2p light elements, we recently extended the same strategy to topological insulators. We demonstrate simultaneous magnetic and hole doping achieved with a single dopant, carbon, in Bi2Se3 by first-principles calculations. Carbon substitution for Se (CSe) results in an opening of a sizable surface Dirac gap (up to 82 meV), while the Fermi level remains inside the bulk gap and close to the Dirac point at moderate doping concentrations. Using a combined theoretical and experimental approach, we reveal the origin of the long-range ferromagnetic coupling in a series of MOFs, constructed from antiferromagnetic dimeric-Cu(II) building blocks. Room temperature ferromagnetism was also observed in Teflon tape (polytetrafluoroethylene) when it is mechanical stretched, cut or heated. Our first-principles calculations revealed that the room temperature ferromagnetism originates from carbon dangling bonds and strong ferromagnetic coupling between them.