Dresden 2011 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 49: CE: Spin Systems and Itinerant Magnets 2

TT 49.13: Talk

Thursday, March 17, 2011, 17:30–17:45, HSZ 03

Exchange driven phonon splitting in transition-metal monoxides — •Christian Kant¹, Franz Mayr², Joachim Deisenhofer², and Alois Loidl² — ¹TU Wien, Wien, Österreich — ²Center for Electronic Correlations, Universität Augsburg, Augsburg, Deutschland

The interplay of magnetism and the underlying crystal lattice is a topical issue of condensed-matter physics. It can relieve frustration in the magnetic sector via a spin-driven Jahn-Teller effect in frustrated lattices, leads to novel excitations such as electromagnons in multiferroics, and bears the potential for future applications via magneto-dielectric effects. A conceptual understanding of the coupling of spins and phonons is, however, often hampered by the complexity of the interactions. For transition-metal monoxides, which are model systems to study the effects of electronic correlations, a magnetism-induced anisotropy in the lattice response was predicted theoretically. We report optical evidence for a linear dependence of the phonon splitting on the nearest-neighbour exchange coupling in the monoxides MnO, Fe_0.92O, CoO and NiO. Our results directly confirm the seminal theoretical prediction of a purely exchange induced splitting of the zone-centre optical phonon and pave a new path for the understanding of spin-phonon coupling effects.