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MA: Fachverband Magnetismus
MA 31: Spin dynamics: Magnetic relaxation and Gilbert damping
MA 31.1: Talk
Wednesday, April 3, 2019, 11:45–12:00, H52
Gilbert damping phenomenology for two-sublattice magnets — •Akashdeep Kamra1, Roberto Troncoso1, Wolfgang Belzig2, and Arne Brataas1 — 1Center for Quantum Spintronics, Department of Physics, Norwegian University of Science and Technology, Trondheim, Norway — 2Department of Physics, University of Konstanz, Konstanz, Germany
We present a systematic phenomenological description of Gilbert damping in two-sublattice magnets. Our theory covers the full range of materials from ferro- via ferri- to antiferromagnets. Following a Rayleigh dissipation functional approach within a Lagrangian classical field formulation, the theory captures intra- as well as cross-sublattice terms in the Gilbert damping, parameterized by a 2×2 matrix. When spin-pumping into an adjacent conductor causes dissipation, we obtain the corresponding Gilbert damping matrix in terms of the interfacial spin-mixing conductances. Our model reproduces the experimentally observed enhancement of the ferromagnetic resonance linewidth in a ferrimagnet close to its compensation temperature without requiring an increased Gilbert parameter. It also predicts new contributions to damping in an antiferromagnet and suggests the resonance linewidths as a direct probe of the sublattice asymmetry, which may stem from boundary or bulk.
Reference: Phys. Rev. B 98, 184402 (2018).