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

Oh, Junseok

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

Description

Title

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

Author(s)

Oh, Junseok

Issue Date

2024-07-10

Director of Research (if dissertation) or Advisor (if thesis)

Mason, Nadya

Doctoral Committee Chair(s)

Lorenz, Virginia

Committee Member(s)

• Gilbert, Matthew
• Hoffmann, Axel

Department of Study

Physics

Discipline

Physics

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

Topological insulator, Magnetoresistance

Abstract

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.

Graduation Semester

2024-08

Type of Resource

Thesis

Handle URL

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

Copyright and License Information

Copyright 2024 Junseok Oh

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