ORCID
https://orcid.org/0009-0003-4395-6491
Year
2025
Season
Summer
Paper Type
Master's Thesis
College
College of Arts and Sciences
Degree Name
Master of Science in Material Science & Engineering (MS)
Department
Physics
NACO controlled Corporate Body
University of North Florida. Department of Physics
Committee Chairperson
Dr. Jason Haraldsen
Second Advisor
Dr. Daniel Santavicca
Third Advisor
Dr. Michael Lufaso
Department Chair
Dr. Gregory Wurtz
College Dean
Dr. Kaveri Subrahmanyam
Abstract
We investigate how anisotropic spin interactions, including Dzyaloshinskii–Moriya and Kitaev terms, manifest across quantum spin systems ranging from a single S = 1/2 dimer to molecular spin clusters and layered magnetic materials. Beginning with an exact analysis of the spin dimer, we demonstrate how singlet–triplet mixing induced by Dzyaloshinskii–Moriya interaction directly influences both thermodynamic observables and inelastic neutron scattering spectra. These microscopic fingerprints are then extended to trimer, tetramer, and tetrahedron geometries, where field-induced phase transitions and heat capacity anomalies reveal the interplay between isotropic Heisenberg and anisotropic Kitaev exchanges. In the frustrated zigzag honeycomb lattice, we show that a competing Heisenberg model alone can reproduce spectral features often attributed to Kitaev physics, emphasizing the importance of geometric frustration and exchange competition. To experimentally evaluate the conditions under which an asymmetric Heisenberg model is applied, we synthesize and characterize $\alpha$-RuCl$_3$ crystals. Structural, magnetic, and spectroscopic measurements confirm that our crystals reproduce the key features of specimens reported in the literature. Raman and susceptibility data demonstrate that stacking faults can be a measure of the DM interactions if the stacking sequence is dictated by spin canting. Moreover, exfoliation suppresses these pathways, driving the system toward a quasi-two-dimensional limit. These results clarify how microscopic spin interactions shape macroscopic behavior and establish a material platform for tuning effective spin Hamiltonians through structural control.
Suggested Citation
Wilson, Evan M., "Frustrated quantum magnetism: The interplay of isotropic and anisotropic interactions with application to α-RuCl3" (2025). UNF Graduate Theses and Dissertations. 1361.
https://digitalcommons.unf.edu/etd/1361
Included in
Condensed Matter Physics Commons, Other Materials Science and Engineering Commons, Quantum Physics Commons