《大湾区物理讲堂 2025-13期》于海明：反铁磁绝缘体中的自旋波传输

• 题目: 反铁磁绝缘体中的自旋波传输
• 主讲人：于海明 @ 北京航空航天大学
• 时间：2025年3月20日 10:00-11:00
• 地点：Room P1078, College of Science

主讲人简介

于海明，北京航空航天大学 集成电路科学与工程学院 教授、博士生导师。2006年本科毕业于北京大学物理学院。2011年博士毕业于瑞士洛桑联邦理工大学（EPFL）。2011-2014年在德国慕尼黑工业大学从事博士后研究。2014年加入北京航空航天大学Albert Fert研究院从事自旋波电子学研究。2015年获海外高层次人才（青年）项目，现任北京航空航天大学教授。主要研究方向：自旋电子学、磁子学、自旋热电子学。

讲座简介

Magnons, the quanta of spin waves, are collective excitations of electron spins in magnetic materials, which do not rely on charge transport, and can thus avoid Joule heating in information processing, making them potential candidates for next-generation low-power spintronic devices. Magnonics [1] conventionally study spin waves in ferromagnetic (e.g., CoFeB) and ferrimagnetic (e.g., YIG) materials. Recently, the study of antiferromagnetic (AFM) spin waves has seen a surge of interests [2]. Hematite (α-Fe₂O₃) is one of the materials where the Dzyaloshinskii-Moriya interaction was first discovered, and may potentially exhibits some unconventional magnetism [3]. Apart from the AFM resonance at THz [4], a low-frequency (~10 GHz) mode was reported in hematite with low magnetic damping comparable to that of YIG (10⁵) [5]. In this talk, I will introduce our observation of long-distance propagation of spin waves in hematite with a high group velocity of up to 22.5 km/s [6]. An exchange stiffness of 1.7 Å is deduced from its dispersion relation. Furthermore, we study the spin-wave propagation in hematite below the Morin temperature, i.e., in its easy-axis phase. We unexpectedly discover a nearly zero-frequency magnon mode, which is theoretically interpreted as gapless magnons within the AFM domain walls [7]. While ferromagnetic magnons are always right-handed, AFM magnons can carry both left-handed and right-handed chirality. Finally, we provide direct experimental observation of AFM magnon interference with alternating chirality, which enables the control over the sign of pure spin current in the antiferromagnetic insulator [8].

海报链接