Microscopic origin of subthermal magnons and the spin Seebeck effect

Abstract

Recent experimental evidence points to low-energy magnons as the primary contributors to the spin Seebeck effect. This spectral dependence is puzzling since it is not observed on other thermocurrents in the same material. Here, we argue that the physical origin of this behavior is the magnon-magnon scattering mediated by phonons, in a process which conserves the number of magnons. To assess the importance and features of this kind of scattering, we derive the effective magnon-phonon interaction from a microscopic model, including band energy, a screened electron-electron interaction and the electron-phonon interaction. Unlike higher order magnon-only scattering, we find that the coupling with phonons induce a scattering which is very small for low-energy (or subthermal) magnons but increases sharply above a certain energy -- rendering magnons above this energy poor spin-current transporters.

9 pages, 3 figures

References in corpus (6)

• Observation of the Spin-Seebeck Effect in a Ferromagnetic Semiconductor
• Markovian Master Equations: A Critical Study
• Critical suppression of spin Seebeck effect by magnetic fields
• Magnon Mediated Electric Current Drag Across a Ferromagnetic Insulator Layer
• The effect of the magnon dispersion on the longitudinal spin Seebeck effect in yttrium iron garnets (YIG)
• Magnetic field dependence of the magnon spin diffusion length in the magnetic insulator yttrium iron garnet

Cited by in corpus (6)

• Origin of the thickness-dependent low-temperature enhancement of spin Seebeck effect in YIG films
• Thermally Driven Long Range Magnon Spin Currents in Yttrium Iron Garnet due to Intrinsic Spin Seebeck Effect
• Thermodynamic transport theory of spin waves in ferromagnetic insulators
• Magnetic-field-induced suppression of spin Peltier effect in Pt/${\mathrm{Y}}_3\mathrm{F}{\mathrm{e}}_5{\mathrm{O}}_{12}$ system at room temperature
• Temperature dependence of the Spin Seebeck effect in a mixed valent manganite
• Spin Peltier effect and its length scale in Pt/YIG system at high temperatures