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Exploring Spin and Topological Phenomena in Complex Oxide Thin Films: Nano Seminar series
October 29, 2021 @ 2:00 pm - 3:00 pm
Prof. Yuri Suzuki, Stanford University, Applied Physics
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 Gilbert damping parameter as as low as ~ 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. 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 these ultra-thin oxide spinels, making them also promising for information storage.
Yuri Suzuki did her PhD at Stanford and spent a few years in MSE here at UCB (Go Bears!) before joining their faculty in Applied Physics and the Geballe Lab.