Author ORCID Identifier:

https://orcid.org/0009-0006-8373-4529

Date of Graduation

9-2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Physics (PhD)

Degree Level

Graduate

Department

Physics

Advisor/Mentor

Jin Hu

Committee Member

Hiro Nakamura

Third Committee Member

Hugh O. H Churchill

Keywords

Gigantic magnetoresistance; Layered Magnetic Materials; Topological Materials

Abstract

The discovery of topological materials (TMs) has opened up exciting opportunities for probing fundamental physics and enhancing innovative device integrations. These materials display various exotic properties, such as large magnetoresistance, high mobility, chiral anomaly, and surface Fermi arcs. The magnetic versions of ZrSiS family, LnSbTe and LnPS (Ln = lanthanide) have attracted intensive attention as these materials provide a new platform to study interplay between magnetism, topological states, and electron correlations. The vast pool of topological materials has provided exciting avenues to precisely engineer the topological states by modulating spin-orbital coupling, electronic dimensionality, and lattice constant through element substitutions. This research centers on previously less explored magnetic topological materials LnPS (GdPS, SmPS) along with their device fabrication techniques and systematic evolution of off stoichiometric PrSbxTe2-x. The compounds GdPS and SmPS exhibit orthorhombic crystal with distortion in P plane unlike square nets of Sb plane in tetragonal LnSbTe. GdPS displays antiferromagnetic ground state with insulator to metal transition (MIT) leading to gigantic isotropic negative magnetoresistance. With Se inclusion in GdPSxSe1-x, MIT suppresses resulting in more insulating behavior and a subtle degree of anisotropy emerges. Furthermore, the study of the evolution of PrSbxTe2-x reveals the correlation between the gigantic anisotropic negative magnetoresistance and magnetism in x = 0.3 composition.

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