Low-temperature magneto-transport study of topological insulator-magnetic material heterostructures

Topological insulators have been extensively investigated in the field of condensed matter physics. These materials represent a unique class characterized by insulating bulk states and topologically protected surface states, showcasing a strong coupling between momentum and spin. The integration of magnetism with topological insulators has garnered significant attention for potential applications in spintronics and quantum computing. This thesis delves into the examination of two material systems comprising topological insulator-magnetic material heterostructures using low-temperature magneto-transport techniques. The first system consists of a topological insulator, Bi2Se3, and a metallic ferromagnet, Co/Pt multilayer, featuring perpendicular magnetic anisotropy. Despite expectations that topological surface states may be annihilated due to band hybridization, various magnetoresistance phenomena are observed, notably the hysteretic square switching magnetoresistance below 1.3 K. Through comparison with magnetoresistance behaviors of the top ferromagnetic layer, this effect is attributed to induced magnetic ordering within the topological insulator. A proposed mechanism suggests involvement of spin-valve and skyrmions. In the second system, magnetoresistance in Bi2Se3 deposited on a ferrimagnetic insulator, Yttrium Iron garnet, is explored as a function of electrostatic gating. The dependence of magnetic anisotropy of the induced magnetization in the topological insulator on chemical potential is investigated. The experiment aims to manipulate the magnetic anisotropy of induced magnetic ordering through gating. Observed magnetoresistance responses indicate the potential for controlling magnetic anisotropy via gating mechanisms.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2024

Author dc:creator

• Oh, Junseok

Contributors dc:contributor

• Mason, Nadya
• Lorenz, Virginia
• Gilbert, Matthew
• Hoffmann, Axel

• Topological Insulator
• Magnetoresistance

Statement dc:rights

• Copyright 2024 Junseok Oh

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/125577

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F125577