Exploring low-temperature spin dynamics in the doped spinel ferrite Li<sub>0.5</sub>AlFe<sub>1.5</sub>O<sub>4</sub> (LAFO)
ORAL
Abstract
Epitaxial ferrimagnetic insulators are promising platforms for low-dissipation spin transport and coherent magnonics, but their cryogenic performance is often limited by poorly understood spin relaxation. We investigate low-temperature spin dynamics in epitaxial thin films of lithium aluminum ferrite (LAFO) using broadband ferromagnetic resonance (FMR) spectroscopy from 68 K to 0.44 K. LAFO's tunable spinel structure—with magnetocrystalline anisotropy controlled via Al substitution—provides a platform to study intrinsic magnetic properties and defect-driven damping. We measure FMR with the magnetic film aligned along both the [100] and [110] axes. We observe changes in anisotropy and linewidth broadening as a function of temperature, indicating the role of antisite defects as fluctuating spin centers. The emergence of non-monotonic linewidth evolution at low temperatures suggest coupling between magnons and two-level systems (TLS), revealing a previously unexplored damping mechanism in disordered ferrites. These results position LAFO as a model system for studying spin coherence in complex oxides and highlight the importance of defect engineering in low-loss magnetic materials. A companion talk will discuss theoretical modeling of TLS-induced damping.
*This work was supported as part of the Center for Energy Efficient Magnonics an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences at SLAC National Laboratory under contract # DE-AC02-76SF00515 and cryogenic measurements were enabled by the cryostat facility of the Center for Molecular Quantum Transduction, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Award No.DE-SC0021314.
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Presenters
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Srishti Pal
- Cornell University