Physics Colloquium- A Secret of Pumping Iron: Uncovering Mechanisms of Damping

Abstract: Precession of magnetization in all real materials undergoes “damping,” analogous to damped mechanical oscillations with friction. Minimizing magnetic damping is crucial for engineering spintronic devices (e.g., nanoscale magnetic memories and signal generators) that can be operated with low power input. However, the mechanisms of damping in various materials – even in the simplest ferromagnetic metals – have yet to be understood.

In this talk, I will present our recent experimental study that provides fundamental insights into magnetic damping in a simple model system: crystalline thin films of pure iron. Our results reveal – somewhat counterintuitively – that cleaner crystals of iron can exhibit higher damping. This observation cannot be accounted for by the classical eddy current loss, but is instead well explained by a quantum mechanical effect (i.e., intraband scattering). While this fundamental damping mechanism was theoretically proposed more than 40 years ago, our study is the first to confirm it unambiguously for thin films of an elemental ferromagnet. Our findings also give hints for engineering low-damping materials for power-efficient spintronic devices.

Reference: B. Khodadadi, A. Rai, A. Sapkota, et al. Phys. Rev. Lett. 124, 157201 (2020).

Bio:

Satoru Emori is an Assistant Professor in the Department of Physics at Virginia Tech. He received his B.S. in Materials Science and Engineering at the University of California, Irvine in 2008 and Ph.D. in Materials Science and Engineering at the Massachusetts Institute of Technology in 2013. His doctoral thesis work investigated the motion of chiral domain walls in ultrathin metallic ferromagnets. Following his postdoctoral work at Northeastern University and Stanford University, where he studied magnetization dynamics in complex oxide materials, he joined the faculty of Virginia Tech in Fall 2017. His research group [homepage] is focused on spin transport and dynamics in model thin-film materials, ranging from amorphous metals to epitaxial oxides.

Homepage: https://sites.google.com/a/vt.edu/emori/

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