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MA: Fachverband Magnetismus
MA 43: Magnetization / Demagnetization Dynamics III
MA 43.8: Talk
Thursday, March 19, 2015, 11:30–11:45, EB 301
Gilbert-like damping mediated by time retardation in atomistic magnetization dynamics — •Danny Thonig1, Jürgen Henk2, and Olle Eriksson1 — 1Department of Material Theory, Uppsala University, Sweden — 2Martin Luther University Halle-Wittenberg, Halle, Germany
The switching dynamics of atomic magnetic moments is determined by the loss of angular momentum. This damping in the equation of motion correlates a magnetic moment at a time t to its very recent value at a time t − δ t. However, physical events are time retarded; that is, magnetic moments are linked to their state at any t′< t. This raises two questions: 1. How does time retardation affect the evolution of magnetic moments? 2. Could time retardation motivate a damping mechanism proportional to the Gilbert damping?
We consider the time-retarded form of the atomistic Landau-Lifshitz-Gilbert equation that accounts for momentum length conservation. More precisely, various retardation functions are applied to the equation of motion without Gilbert damping. We consider a macrospin model as well as realistic materials, like Fe bulk.
From an analytical model as well as from numerical simulations we establish a damping mechanism proportional to the Gilbert damping. On top of this, we also find higher-order effects, like nutation. Our model and results suggest that the origin of damping and inertia in magnetic systems could be due to time retardation.