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

Yttrium and rare-earth iron garnets (<i>R</i>₃Fe₅O₁₂) are ferrimagnetic insulators that have been widely studied for magnetic and spintronic applications. In this study, we report the thermal conductivity (<i>κ</i>) between 300 and 773 K for the single crystals of<i>R</i>₃Fe₅O₁₂, where<i>R</i>= Y, Gd, Dy, and Yb. For Y₃Fe₅O₁₂, the<i>κ</i>up to the Curie temperature (<i>T</i>_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<i>κ</i>, with Dy₃Fe₅O₁₂showing the smallest values due to the strong interactions of heat-carrying phonons with the crystal field excitations of Dy³⁺ions.