Western Kentucky University
Department of Physics and Astronomy

Colloquium

Dr. Shawn Pollard

Department of Physics and Materials Science
University of Memphis

"Disorder by Design: Controlling Composition in Ferrimagnets for High-Speed, Low-Power Spintronics"

April 13, 2026 @ 4:00 pm in KTH 2038 (Zoom ID: 93595838321)

About the Speaker

https://classic.memphis.edu/physics/faculty-pollard/index.php

Abstract

Spintronics, short for spin transport electronics, has transformed the fields of data storage and information processing. While traditional spintronic devices rely on ferromagnetic materials as their fundamental building blocks, they face intrinsic limitations to speed, energy consumption, and density. As an alternative, antiferromagnets have long been studied as a theoretical substitute allowing for significantly faster speeds. However, challenges in their growth and difficulties in reading their magnetic state have limited their applications. To overcome these limitations, transition metal/rare earth (TM/RE) ferrimagnets have emerged as promising candidate materials, which are compatible with traditional manufacturing and sensing methods used in their ferromagnetic counterparts. In TM/RE ferrimagnets, atoms of the same species ferromagnetically couple to each other, while coupling antiferromagnetically to the other species. In this talk, I will discuss how we can harness and engineer these materials for next-generation devices. First, I will discuss how the antiferromagnetic exchange coupling in TM/RE alloys enables ultrafast, sub-nanosecond magnetization switching and massive domain wall velocities beyond 5 km/s. I will explore the critical role that material growth and atomic-level variations play in these systems, highlighting the need for precise control over the film growth in order to realize these materials full potential. Time permitting, I will also present recent work of ours showing how alloying transition metals with rare-earth elements significantly reduces the material's exchange stiffness, a phenomenon we can directly measure by observing the deformation of nanoscale magnetic vortices in PyGd disks.