Specific heat and thermal conductivity of ferromagnetic magnons in Yttrium Iron Garnet

Abstract

The specific heat and thermal conductivity of an insulating ferrimagnet Y3Fe5O12 (Yttrium Iron Garnet, YIG) single crystal were measured down to 50 mK. The ferromagnetic magnon specific heat Cm shows a characteristic T1.5-dependence down to 0.77 K. Below 0.77 K, a downward deviation is observed, which is attributed to the magnetic dipole-dipole interaction with typical magnitude of . The ferromagnetic magnon thermal conductivity does not show the characteristic T2-dependence below 0.8 K. To fit the data, both magnetic defect scattering effect and dipole-dipole interaction are taken into account. These results provide a complete picture of the thermodynamic and thermal transport properties of the low-lying ferromagnetic magnons.