Phonon thermodynamics of rare-earth-iron Laves phases below and above the Curie temperature

The cubic rare-earth-iron Laves phases (C15 structure) have been studied extensively because of the useful magnetic and magneto-mechanical properties of its members, particularly giant magnetostriction, but less attention has been paid to interactions between the magnetism and the phonons. We investigated several thermal properties of YFe2, ErFe2 and TbFe2 in the quasiharmonic approximation via both spin-polarized and non-spin polarized density functional theory calculations and obtained phonon dispersions and phonon density of states (DOS) curves below and above the Curie temperature. Comparison to measurements of the Fe-specific phonon DOS curves of the materials obtained via nuclear resonant inelastic x-ray scattering suggests that the quasiharmonic model does not completely encapsulate the physics of these systems.