Heat transport in insulator/ferromagnetic-insulator/insulator heterogeneous nanostructures at low temperatures

A kinetic approach to the heat transport by phonons and magnons through a ferromagnetic insulator (FI) layer located between two massive insulators $({I}_{1}$ and ${I}_{2})$ is analytically considered. The effective transverse heat conductivity of such a layered system with an arbitrary thickness of the FI layer is calculated, and the thickness at which the size effect is manifested in the thermal conductivity is found.