Description
- Abstract:
- The Giant Spin Hall Effect (GSHE) in certain transition metals due to strong spin-orbit interaction has shown great potential in the development of novel spintronic devices, such as magnetic random access memories and spin-logic devices. The induced spin current in a thin film with GSHE imposes a spin-transfer-torque (STT) on an adjacent ferromagnetic layer, strong enough to switch the magnetization direction. In this work, we realized robust perpendicular magnetic anisotropy (PMA) in a layered structure combining various GSHE solids with ultrathin ferromagnetic films. We have achieved a critical current density of 2×10^6A/cm^2 to switch the magnetization vector direction. Utilizing a macro spin model, we have determined the spin Hall angles of beta-Tungsten and beta-Tantalum to be -0.40 (in the bulk limit) and -0.11 at room temperature, respectively. These numbers are among the largest in transition-metal-based solids. Furthermore, we have investigated the thickness and temperature dependence of the GSHE, which has revealed appealing characteristics of strong spin-orbit interaction and the mechanism leading to GSHE. Next, we focus on Anomalous Hall Effect (AHE) which is also caused by the strong spin-orbit coupling. We have fabricated and studied Fe-Pt alloy thin films with varying concentrations and thicknesses. We have observed AHE with a very large Hall slope. Our systematic study on the magnetic and transport properties reveals the intrinsic and side-jump mechanisms that contribute to the AHE in Fe-Pt alloy system. Due to its metallic nature, the low-frequency electronic noise in Fe-Pt based Hall sensor is two orders of magnitude lower than that of some semiconductor Hall sensors. Finally, we have studied another type of spintronic device called magnetic tunnel junction (MTJ) using rapid electron transport measurement. We have observed voltage controlled magnetic anisotropy in MTJs. The physics is likely due to the field effect of spin-orbit coupling within the interfacial regions in the MTJ multilayered structure. We believe the integration of MTJ with GSHE structure could open the door for future spintronic applications.
- Notes:
- Thesis (Ph.D. -- Brown University (2016)
Access Conditions
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Citation
Hao, Qiang,
"Giant Spin Hall Effect and Anomalous Hall Effect in Solids with Strong Spin-Orbit Coupling"
(2016).
Physics Theses and Dissertations.
Brown Digital Repository. Brown University Library.
https://doi.org/10.7301/Z0V69H0H
