Basic Chemistry & Physics

Magnetic Frustration and Low-Dimensional Magnetism in Transition Metal Fluorophosphates and Square-Lattice Intermetallic Compounds

PhD: Stefanie Siebeneichler, Stockholm University (2022)

This project investigated the origin of magnetic frustration and low-dimensional magnetism in transition-metal fluorophosphates and intermetallic compounds where the magnetic ions form triangular or square lattices. Using powder neutron diffraction (PND) together with magnetization, heat capacity measurements, and density functional theory (DFT) calculations, the research revealed how competing magnetic interactions give rise to non-collinear and incommensurate spin structures such as helical, canted ferromagnetic, and spin-vortex crystal states.

Neutron scattering played a central role in determining magnetic ordering and phase transitions at different temperatures, providing insights into how crystal structure topology governs the emergence of frustration and low-dimensional behavior. The findings deepened the understanding of complex magnetic ground states in solids, contributing to the broader field of quantum magnetism and correlated materials research.

Stefanie Siebeneich lerearned a BSc in Metallurgical and Materials Engineering from Istanbul Technical University and completed her MSc in Metallurgical Engineering at RWTH Aachen University in 2017. During her master’s studies, she focused on understanding deformation and phase-transformation mechanisms in high-manganese steels, using ex situ and in situ synchrotron X-ray diffraction as well as small-angle neutron scattering to study microstructure evolution and Mn–C clustering.