Non Local Spin Diffusion Driven by Spin Hall Effect at Oxide Heterointerfaces

Abstract

This thesis describes spin Hall effect (SHE) / Inverse spin Hall effect (ISHE) induced non-local spin transport and detection through a LAO/STO 2-dimensional interface. For that, first this thesis introduce about basic knowledge of spintronics with regard to spin transport, injection and detection. Also spin orbit coupling (SOC) and related effect with Rashba SOC which is closely related to the experimental results will be described intensively. The physical origin of SHE/ISHE is discussed based on intrinsic and extrinsic mechanism followed by the previous experimental works done in various systems. Then, 2-dimentional electron gas of LaAlO3/SrTiO3(LAO/STO) interface and its interesting phenomenon are introduced along with recent research progress, which shows that the LAO/STO is exciting playground for spin-orbitronics. For the main part of this thesis, our experimental scheme of the non-local measurement for the spin diffusion and precession through the SHE/ISHE is first described. Next, detailed sample preparation, patterning and fabrication method are explained. The fabricated H-bar type geometry device can manipulate spin current without spin injection from ferromagnetic material and detect through same material (LAO/STO 2DEG H-bar geometry). Generating a spin current not through the spin injection from outside but instead through the inherent spin Hall effect and demonstrating the non-local spin transport is a novel approach for spintronic application with 2DEG materials. The analysis on the nonlocal spin voltage, confirmed by the signature of a Larmor spin precession and its length dependence, displays that both D’yakonov-Perel’ and Elliott-Yafet mechanisms involve in the spin relaxation at low temperature. Our results show that the oxide heterointerface is highly efficient in spin-charge conversion with exceptionally strong spin Hall coefficient γ ~ 0.15 ± 0.05 and could be outstanding platform for the study of coupled charge and spin transport phenomena and their electronic applications.