High-temperature thermal conductivity of yttrium and rare-earth iron garnets

Yttrium and rare-earth iron garnets ( R 3 Fe 5 O 12 ) are ferrimagnetic insulators that have been widely studied for magnetic and spintronic applications. In this study, we report the thermal conductivity (κ ) between 300 and 773 K for the single crystals of R 3 Fe 5 O 12 , where R = Y, Gd, Dy, and Yb. For Y 3 Fe 5 O 12 , the κ up to the Curie temperature ( T C ≈ 555 K) can be described well with a pure phononic model, without considering conduction or scattering by the magnons. The iron garnets containing magnetic rare-earth ions exhibit smaller κ , with Dy 3 Fe 5 O 12 showing the smallest values due to the strong interactions of heat-carrying phonons with the crystal field excitations of Dy 3+ ions.