| Author: | Li, Peigen |
| Title: | Bulk and interfacial nature of spin hall magnetotransport with iron garnet heterostructures |
| Advisors: | Leung, Chi Wah (AP) |
| Degree: | Ph.D. |
| Year: | 2025 |
| Subject: | Spintronics -- Materials Magnetic materials Heavy metals Hong Kong Polytechnic University -- Dissertations |
| Department: | Department of Applied Physics |
| Pages: | xv, 155 pages : color illustrations |
| Language: | English |
| Abstract: | Artificial intelligence technologies have put forward more stringent requirements for information storage devices. Compared with electronic devices made of traditional semiconductor materials, spintronic devices have advantages such as low energy dissipation and fast writing and reading of data. Taking the device composed of magnetic insulator (MI) and heavy metal (HM) as an example. Due to the low damping of MI and its ability to transmit spin information through magnon, combined with the spin orbit coupling effect of MI/HM, high energy efficiency can be achieved with extremely low Ohmic losses. Therefore, such devices are expected to be widely adopted in the next-generation storage devices. The spin transport mechanism of MI/HM systems is complicated, especially for heterostructure composed of platinum (Pt) and ferrimagnetic rare earth iron garnet (REIG) with compensation phenomenon, which leads to anomalous spin magnetotransport behavior and has attracted much attention. This thesis is based on the study of magnetic and electrical properties of the Tb3Fe5O12 (TbIG)/Pt systems, including the magnetization compensation behavior, the presence of two sign cross-over points in anomalous Hall effect resistance (RAHE) vs. temperature plot, the impact of REIG/HM interface and REIG bulk on spin magnetotransport. Specifically, the content is organized as follows: The first part introduces the influence of ultra-thin garnet-like spacers (Y3Al5O12 (YAG) and Gd3Ga5O12 (GGG)) on the spin magnetotransport of TbIG/Pt system. Hall devices are fabricated by pulsed laser deposition (PLD), magnetron sputtering (MS), and photolithography, and the influence of different spacer thicknesses on magnetic proximity effect (MPE) and spin Hall transport are studied. Then, I construct a bilayer REIG system composed of TbIG and Eu3Fe5O12 (EuIG). A thickness-dependent compensation temperature (Tcomp) is realized by changing the thickness of EuIG. The exchange coupling between TbIG and EuIG is analyzed, and the effect on two RAHE sign cross-over points is systematically presented. Finally, I introduce the REIG bulk effect on spin transport, by investigating a REIG sandwich structure based on TbIG and EuIG. It is realized through modulating the individual layer thickness of TbIG/EuIG/TbIG/Pt with fixed total thickness. As TbIG gradually moves away from the Pt, the different contributions of REIG/Pt interface and REIG bulk on two RAHE cross-over points are discussed. |
| Rights: | All rights reserved |
| Access: | open access |
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