Date of Graduation

8-2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Physics (PhD)

Degree Level

Graduate

Department

Physics

Advisor/Mentor

Hu, Jin

Committee Member

Churchill, Hugh O.H.

Second Committee Member

Nakamura, Hiro

Keywords

2D magnetism; Magnetic material; Non-trivial spin texture; Physics; Topological hall effect

Abstract

Two-dimensional magnetic materials (2DMMs) have gained significant interest due to their potential for novel physical phenomena and device applications. Mn2-xZnxSb, with its tunable magnetic properties and stable tetragonal layered structure, offers a rich platform for exploring these phenomena. The introduction of Zn into the Mn2Sb lattice efficiently tunes magnetic and electronic properties, making it a compelling candidate for high-performance spintronic devices. With this motivation, we synthesized Mn2-xZnxSb (0 ≤ x ≤ 1) single crystals using a flux method. Mn2Sb exhibits ferrimagnetic order below 550 K with antiparallel spins aligned along the c-axis for two Mn magnetic sublattice Mn(I) and Mn(II), and a spin reorientation occurring below 240 K. Zn substitute the Mn(II) site and the complete substitution of Mn(II) sublattice makes it MnZnSb, which is ferromagnetic with a Curie temperature Tc ~ 310 K. Electronic transport measurements highlight a strong coupling between magnetism and electronic properties in Mn2-xZnxSb. Notably, two groups of distinct electronic transport properties of various compositions, separated by a critical Zn composition of x = 0.6, are discovered. Moreover, Mn2-xZnxSb exhibits composition and temperature dependent topological Hall effect (THE), indicative of complex spin textures like skyrmions providing insights into the interplay between spin, charge, and lattice degrees of freedom in this material. The discovery of THE enhances the potential of Mn2-xZnxSb for applications in spintronic devices. The combination of high-temperature ferromagnetism, tunable electronic and magnetic properties make Mn2-xZnxSb a promising candidate for future research and development in spintronics and quantum technologies. The findings of this research contribute to a deeper understanding of 2DMMs and pave the way for the advancement of new magnetic device.

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