Generalized two-temperature model for coupled phonon-magnon diffusion

Abstract

We generalize the two-temperature model [Sanders and Walton, Phys. Rev. B, 15, 1489 (1977)] for coupled phonon-magnon diffusion to include the effect of the concurrent magnetization flow. Working within the framework of Boltzmann transport equation, we derive the constitutive equations for coupled phonon-magnon transport driven by gradients of both temperature and external magnetic fields, and the corresponding conservation laws. Our equations reduce to the original Sanders-Walton two-temperature model under a uniform external field, but predict a new magnon cooling effect driven by a non-uniform magnetic field in a homogeneous single-domain ferromagnet. We estimate the magnitude of the cooling effect in yttrium iron garnet, and show it is within current experimental reach. With properly optimized materials, the predicted cooling effect can potentially supplement the conventional magnetocaloric effect in cryogenic applications in the future.

17 pages, 6 figures

References in corpus (6)

• Spin Seebeck insulator
• Observation of the Spin-Seebeck Effect in a Ferromagnetic Semiconductor
• Theory of magnon-driven spin Seebeck effect
• Thermal Spin-Transfer Torques in Magnetoelectronic Devices
• Heat conduction in low-dimensional quantum magnets
• Spin Pumping of Current in Non-Uniform Conducting Magnets