题目：A new route towards low-field and room-temperature colossal magnetoresistance

报告人：沈健

邀请人：常凯

时间：2024年11月1日（周五）上午10:30

地点：紫金港校区海纳苑8幢215报告厅

摘要：

From anisotropic magnetoresistance (AMR) to giant magnetoresistance (GMR) and to the state-of-the-art tunneling magnetoresistance (TMR), every order of magnitude increase of MR has set a milestone and advanced the field of spintronics leaping forward. It is thus not surprising that the observation of colossal magnetoresistance (CMR) in manganites, which exhibits at least 3 orders of magnitude larger MR value than that of TMR, has generated great interest with the hope of setting the next milestone in spintronics. However, the fact that CMR requires large field and occurs below room temperature has greatly limits its impact. Since the origin of CMR is directly tied to the field-driven percolation of electronic phase separated (EPS) domains, it is critical to understand the physical origin of EPS and its percolation dynamics in order to lower the field and increase the temperature of CMR. Using oxides superlattice growth with atomic precision, we have successfully fabricated manganites with full chemical order, i.e. all the chemical dopants are spatially ordered. Comparing the conventional and chemically ordered manganites, we have uncovered the origin of EPS as the dopants induced disordering in the system, resolving decades long debate in the field. We have further observed that the energy required for EPS domain growth is much less that for EPS domain nucleation, and magnetic nanodot can assist EPS domain nucleation via exchange field. Moreover, we have successfully grown large-sized and atomically unform manganite thin films using laser scanning technique and raised the critical temperature of manganites over room temperature by strain engineering. Based on these achievements, we have paved a new route towards the realization of low-field and room temperature CMR, which is critical for the next leap of the field of spintronics.

个人简介：

沈健，国家杰青（B类，2007）、国家特聘专家（2009）、美国物理学会会士（Fellow， 2011），复旦大学“浩清”讲席教授（2009），曾任复旦大学物理系主任（2010-2020），现任复旦大学应用表面物理国家重点实验室主任、微纳电子器件与量子计算机研究院院长、微纳加工公共实验室主任、中国物理学会磁学专委会主任。曾获德国马普学会Otto-Hahn奖章、美国能源部杰出青年科学家奖、美国总统青年科技奖（PECASE）。长期从事低维磁性、自旋电子学及其在存储与智能计算中的应用，在包括APS、MRS、AVS、MMM、Intermag等重大国际会议上做邀请报告130余次（含大会报告9次）。