Magnetoresistance effects in metallic antiferromagnets

Antiferromagnets are drawing significant interest as alternatives to ferromagnets in designing faster and more robust memory devices. Recent theoretical and experimental advances show that antiferromagnets can be readily detected and manipulated owing to their diverse crystal and magnetic structures. Moreover, the complexity of antiferromagnetic crystal structures makes antiferromagnets an excellent platform for exploring new topological phenomena. Given the growing interest in antiferromagnets, metallic antiferromagnets can be useful as active spintronics materials due to their high electrical and thermal conductivities and their ability to host strong interactions between charge transport and magnetic spin textures. The work in this thesis is focused on characterizing the magnetoresistance of various metallic antiferromagnets to better understand the relationship between metallic conductivity and spin textures in these materials. Specifically, we studied anisotropic magnetoresistance (AMR) and unidirectional magnetoresistance (UMR) in metallic antiferromagnets. First, in a collinear antiferromagnet FeRh, we found that antiferromagnetic spin canting induced by the external magnetic field can modify the band structure and give rise to an intriguing evolution of the AMR. Moreover, we found that field-induced antiferromagnetic spin canting in FeRh can also induce UMR in the FeRh/Pt bilayer, one of the early reports of UMR in antiferromagnetic systems. Continuing from the UMR studies in FeRh/Pt bilayers, we also observed a UMR effect in noncollinear antiferromagnet Mn3Pt/Ru bilayers, which may include a new type of UMR arising from the noncollinear antiferromagnetic order (anomalous UMR). Finally, in an exfoliated flake of antiferromagnet Fe1/3NbS2, which exhibits both antiferromagnetic order and spin glass, we found that AMR can effectively probe the coexisting, coupled magnetic orders in mesoscopic devices. The work in this thesis has demonstrated novel magnetoresistance effects in metallic antiferromagnets that arise from the complexity of antiferromagnetic crystal structures. We hope the work in this thesis can provide insights into the interplay of metallic conductivity and antiferromagnetic orders and motivate further studies of novel magnetoresistance phenomena in metallic antiferromagnets.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Shim, Soho

Contributors dc:contributor

• Mason, Nadya
• Hoffmann, Axel
• Bradlyn, Barry
• Mahmood, Fahad

• antiferromagnetism
• charge transport

Statement dc:rights

• Copyright 2024 Soho Shim

Language dc:language

en

Handle dc:identifier

https://hdl.handle.net/2142/129478

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/129478