Spin Waves in Ferromagnetic Insulators Coupled via a Normal Metal
arXiv:1407.0635 · doi:10.1103/PhysRevB.90.094418
Abstract
Herein, we study the spin-wave dispersion and dissipation in a ferromagnetic insulator--normal metal--ferromagnetic insulator system. Long-range dynamic coupling because of spin pumping and spin transfer lead to collective magnetic excitations in the two thin-film ferromagnets. In addition, the dynamic dipolar field contributes to the interlayer coupling. By solving the Landau-Lifshitz-Gilbert-Slonczewski equation for macrospin excitations and the exchange-dipole volume as well as surface spin waves, we compute the effect of the dynamic coupling on the resonance frequencies and linewidths of the various modes. The long-wavelength modes may couple acoustically or optically. In the absence of spin-memory loss in the normal metal, the spin-pumping-induced Gilbert damping enhancement of the acoustic mode vanishes, whereas the optical mode acquires a significant Gilbert damping enhancement, comparable to that of a system attached to a perfect spin sink. The dynamic coupling is reduced for short-wavelength spin waves, and there is no synchronization. For intermediate wavelengths, the coupling can be increased by the dipolar field such that the modes in the two ferromagnetic insulators can couple despite possible small frequency asymmetries. The surface waves induced by an easy-axis surface anisotropy exhibit much greater Gilbert damping enhancement. These modes also may acoustically or optically couple, but they are unaffected by thickness asymmetries.
arXiv comment13 pages, 5 figures
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Cited by in corpus (8)
- Spin waves in coupled YIG/Co heterostructures
- Theory of spin Hall magnetoresistance (SMR) and related phenomena
- Chiral excitation of spin waves in ferromagnetic films
- Pure spin currents in magnetically ordered insulator/normal metal heterostructures
- Influence of magnetic surface anisotropy on spin wave reflection from the edge of ferromagnetic film
- Magnetization damping in noncollinear spin valves with antiferromagnetic interlayer couplings
- Nonlocal damping of spin waves in a magnetic insulator induced by normal, heavy, or altermagnetic metallic overlayer: A Schwinger-Keldysh field theory approach
- Anomalous Feedback and Negative Domain Wall Resistance