Regensburg 2019 – wissenschaftliches Programm
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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur
KFM 7: Multiferroics
KFM 7.3: Vortrag
Montag, 1. April 2019, 15:40–16:00, H47
Low frequency phonons in rare-earth langasites — •Lorenz Bergen1, Lukas Weymann1, Andrei Pimenov1, Artem Kuzmenko2, Alexander A. Mukhin2, and Evan Constable1 — 1Institute of Solid State Physics, Vienna University of Technology, 1040 Vienna, Austria — 2Prokhorov General Physics Institute, Russian Academy of Sciences, 119991 Moscow, Russia
Rare-earth langasites are characterized by geometric magnetic frustration exhibiting magneto-electric effects, high piezoelectric properties, and may even support a spin-liquid ground state. To better understand the interplay between the structural and magnetic degrees of freedom it is important to study the phonon and crystal electric field spectra that can be observed in the far infrared (FIR) range. The langasite structure crystallizes in the P321 space group with a general formula A3BC3D2O14. Our study presents spectra of the rare-earth langasite N3Ga5SiO14 using far-infrared reflection spectroscopy. Experiments have been performed with polarized radiation along different crystallographic axes and under different sample temperatures. Phonon excitations at unusually low frequencies are observed that brings the crystal structure of langasites close to a lattice instability. The results of neodymium and holmium-substituted langasites will be compared with the pure La3Ga5SiO14 langasite compound that does not show effects like magnetic frustration.