Magneto-elastic waves in quantum magnets and the full elasticity tensor from thermal diffuse scattering

Orateur : Björn WEHINGER (Department of Quantum Matter Physics, University of Geneva)

In the first part of my presentation I will focus on the triangular lattice Heisenberg antiferromagnet LiCrO2 which exhibits a surprisingly strong magnon-phonon coupling. Using inelastic x-ray scattering we show that phonon dispersion contain so-far undetect ed magnetic correlations that can be probed throughout the Brillouin zone. Our study reveals intrinsic details of the magnetoelastic excitation spectrum. We found single particle excitations with momentum dependent lifetime and continuum scattering at low temperature. Moreover, we observed over-damped modes, para-electromagnons, above the Néel temperature [1]. The second part of my presentation addresses a novel and fully quantitative analysis of thermal diffuse x-ray scattering. I will show that high-precision measurements of diffuse scattering intensities together with a rigorous data analysis allow the determination of the full elasticity tensor in a single crystal diffraction experiment [2]. This approach enables a reliable and model-free determination of the elastic properties and can be performed together with crystal structure investigation in the same experiment.

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