Anomalous optical phonons in FeTe chalcogenides: Spin state, magnetic order, and lattice anharmonicity

V. Gnezdilov, Yu. Pashkevich, P. Lemmens, A. Gusev, K. Lamonova, T. Shevtsova, I. Vitebskiy, O. Afanasiev, S. Gnatchenko, V. Tsurkan, J. Deisenhofer, A. Loidl
2011 Physical Review B  
Polarized Raman-scattering spectra of non-superconducting, single-crystalline FeTe are investigated as function of temperature. We have found a relation between the magnitude of ordered magnetic moments and the linewidth of A1g phonons at low temperatures. This relation is attributed to the intermediate spin state (S=1) and the orbital degeneracy of the Fe ions. Spin-phonon coupling constants have been estimated based on microscopic modeling using density-functional theory and analysis of the
more » ... cal spin density. Our observations show the importance of orbital degrees of freedom for the Fe-based superconductors with large ordered magnetic moments, while small magnetic moment of Fe ions in some iron pnictides reflects the low spin state of Fe ions in those systems.
doi:10.1103/physrevb.83.245127 fatcat:ibxzjr3cuvhcrnu5z5ha36rywy