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MS&E Seminar Series: Dr. Yuri Suzuki

April 7 @ 4:00 PM 5:00 PM

Professor Yuri Suzuki
Stanford University
Host: Jun Xiao (MS&E)

New Materials for Spin Wave Spintronics: Spin and Topological Phenomena in Low Loss Ferromagnetic Insulator Thin Films

Abstract
Spin functionality in materials has the potential to transform energy relevant technologies by providing a new approach to information propagation and manipulation. To date, microelectronics has been largely based on the manipulation of electrons via their charge and advances in devices have been enabled by the introduction of new materials and their subsequent improvements in performance. Spin functionality has been exploited to a limited extent in microelectronics via the flow of spin-polarized charge current where there is flow of both net charge and spin, thereby having the same power dissipation issues as charge current. However more recently, pure spin currents based on the flow of angular momentum via spin waves, or magnons, have been identified as a new medium for information propagation and manipulation. A spin-wave-based electronics based on ferromagnetic insulators where information can be transported and manipulated without charge current would provide a new paradigm for low energy consumption computing. However, insulating behavior is not a sufficient requirement for low damping, as shown by the very limited options for low-damping insulators.

We have developed a new class of low loss spin ferrite thin films with Gilbert damping parameter as low as a ~ 0.0006 and negligible inhomogeneous linewidth broadening, resulting in narrow half-width half-maximum linewidths. The most promising spinel ferrite films are of the compositions Mg(Al,Fe)2O4 and Li0.5(Al,Fe)2.5O4. We have also demonstrated efficient spin pumping from these spinel ferrites into an adjacent heavy metal layer through measurement of the spin-mixing conductance, Gilbert damping enhancement and electrical voltage peaks that appear at ferromagnetic resonance. Spin-torque ferromagnetic resonance measurements indicate that we can indeed achieve electrical control of magnetization. We have also demonstrated current induced spin-orbit torque switching of the ferrite magnetization with spin-to-charge interconversion in Pt that is significantly larger than previous studies. We have also combined these ferrite thin films with topological insulators to demonstrate spin pumping as well as spin torque ferromagnetic resonance. This new class of epitaxial spinel ferrite materials is promising for future low-power electronics such as spin-wave logic devices, voltage controlled magnetic memory and magnonic waveguides. More recently we have discovered evidence for skyrmions in ultra-thin oxide spinel ferrite films, making them also promising for information storage.

Biography
Yuri Suzuki is a professor in the Department of Applied Physics at Stanford University. She received an A.B. in Physics from Harvard (1989)and a Ph.D. in Applied Physics from Stanford (1995). She did her postdoctoral work at Bell Laboratories. Before arriving at Stanford, she was an assistant and associate professor at Cornell (1997-2002) and associate and full professor at Berkeley (2002-2012) both in Materials Science and Engineering. Her research focuses on emergent behavior in strongly correlated oxide systems, with recent emphasis on oxide interfaces and spin current generation and control. Her awards and recognition include the DoD Vannevar Bush Faculty Fellowship, APS Fellowship, Maria Goeppert-Mayer Award, Packard Foundation Fellowship, NSF CAREER Award and ONR Young Investigator Award.