Angular momentum conservation and phonon spin in magnetic insulators

We develop a microscopic theory of spin-lattice interactions in magnetic insulators, separating rigid-body rotations and the internal angular momentum, or spin, of the phonons, while conserving the total angular momentum. In the low-energy limit, the microscopic couplings are mapped onto experimentally accessible magnetoelastic constants. We...

Magnon-polaron transport in magnetic insulators

We theoretically study the effects of strong magnetoelastic coupling on the transport properties of magnetic insulators. We develop a Boltzmann transport theory for the mixed magnon-phonon modes ("magnon polarons") and determine transport coefficients and the spin diffusion length. Magnon-polaron formation causes anomalous features in the...

Magnon polarons in the spin seebeck effect

Sharp structures in the magnetic field-dependent spin Seebeck effect (SSE) voltages of Pt/Y3Fe5O12 at low temperatures are attributed to the magnon-phonon interaction. Experimental results are well reproduced by a Boltzmann theory that includes magnetoelastic coupling. The SSE anomalies coincide with magnetic fields tuned to the threshold of...

Magnon spin transport driven by the magnon chemical potential in a magnetic insulator

We develop a linear-response transport theory of diffusive spin and heat transport by magnons in magnetic insulators with metallic contacts. The magnons are described by a position-dependent temperature and chemical potential that are governed by diffusion equations with characteristic relaxation lengths. Proceeding from a linearized...