Influence of randomness and retardation on the FMR-linewidth

Abstract

The theory predicts that the spin-wave lifetime ${\tau }_L$ and the linewidth of ferromagnetic resonance $\Delta B$ can be governed by random fields and spatial memory. To that aim the effective field around which the magnetic moments perform a precession is superimposed by a stochastic time dependent magnetic field with finite correlation time. The magnetization dynamics is altered by inclusion of a spatial memory effect monitoring a non-local interaction of size $\xi$. The underlying Landau-Lifshitz-Gilbert equation (LLG) is modified accordingly. The stochastic LLG is equivalent to a Fokker-Planck equation which enables to calculate the mean values of the magnetization vector. Within the spin-wave approximation we present an analytical solution for the excitation energy and its damping. The lifetime and the linewidth are analyzed depending on the strength of the random field $D$ and its correlation time ${\tau }_c$ as well as the retardation strength ${\Gamma }_0$ and the size $\xi$. Whereas ${\tau }_L$ decreases with increasing $D$, retardation strength ${\Gamma }_0$ and ${\tau }_c$, the lifetime is enhanced for growing width $\xi$ of the spatial retardation kernel. In the same manner we calculate the experimentally measurable linewidth $\Delta B$ is increased strongly when the correlation time ${\tau }_c$ ranges in the nanosecond interval.

20 pages, 4 figures

References in corpus (5)

• Spin Torque Ferromagnetic Resonance Induced by the Spin Hall Effect
• Identification of the dominant precession damping mechanism in Fe, Co, and Ni by first-principles calculations
• Dynamic approach for micromagnetics close to the Curie temperature
• Time-resolved detection of spin-transfer-driven ferromagnetic resonance and spin torque measurement in magnetic tunnel junctions
• Thermal fluctuations and longitudinal relaxation of single-domain magnetic particles at elevated temperatures

Cited by in corpus (2)

• Mitigation of rare events in multistable systems driven by correlated noise
• Nonlocal feedback in ferromagnetic resonance