Date of Award

2026

Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy in Physics (PhD)

Administrative Home Department

Department of Physics

Advisor 1

Ranjit Pati

Committee Member 1

Yongmei M. Jin

Committee Member 2

Ravindra Pandey

Committee Member 3

Issei Nakamura

Abstract

Van der Waals (vdW) magnets have been of great interest for advancing low- dimensional spintronics. A notable example is the quasi-one-dimensional (Q1D) vdW CrSbSe3, as it is composed of individual one-dimensional units that are held together by the vdW forces. Finding other Q1D vdW magnets that exhibit non-metallic behavior together with long range ferromagnetic ordering is critical in developing next generation spintronics. Here in, using first-principles density functional theory (DFT), we investigate the compositional effects on electronic and magnetic behavior of Cr1–xMnxSbSe3 (x = 0, 0.5, 1). When 50% of Cr is replaced with Mn in Cr1–xMnxSbSe3, it transitions from a ferromagnetic semiconductor (x=0) to a ferromagnetic half-metal (x=0.5), and then to an antiferromagnetic metal (x=1) for a complete replacement of Cr with Mn. The predicted magnetic ordering can be attributed to super-exchange in the case of CrSbSe3, while the Ruderman-Kittel-Kasuya-Yosida exchange interaction is responsible for the ferromagnetic and antiferromagnetic ordering in the half-metallic and metallic system, respectively. The Curie temperature (TC ) was predicted for x=0 and x=0.5 using a Monte Carlo algorithm that uses the Heisenberg spin Hamiltonian to predict thermally activated spin depolarization. We then studied the structure–property relationship in a newly designed CrBiTe3. The change in electronegativity and strong relativistic effects due to the incorporation of Bi leads to strengthening of the second nearest intra-unit and inter-unit exchange interactions of the system. The plausible cause for this unusual behavior is attributed to the relativistic Bi atom that causes a distortion in the electron density arising from the hybridization of the py–py orbitals of the intra-unit Te and Bi, respectively, leading to a higher TC value of ∼ 170 K. Following this endeavor, the spin selectivity of a one-dimensional CrSbSe3 magnet was investigated in a device configuration. A quantum transport approach was used to study the spin-transport properties. A high spin injection factor of 100% up to a bias of ∼ 0.6 eV was observed in the one-dimensional CrSbSe3 spin filter.

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