Speaker
Sophie de Brion
(Institut Néel, CNRS-UJF)
Description
S. de Brion1, F. Levy-Bertrand1, R. Ballou1, V. Simonet1, P. Lejay1, J-B. Brubach2 and P. Roy2
1 Institut Néel, CNRS et Université Joseph Fourier, BP 166, F-38042 Grenoble Cedex 9, France 2 SOLEIL Lorme des Merisiers, Saint Aubin 09192 Gif sur Yvette, France
For the first time, down to low temperature (from 300 K to 5 K), successful terahertz measurements (from 8 to 60 cm-1) have been performed on the AILES synchrotron line at SOLEIL. Those measurements were realized on the iron-langasite single crystals Ba3(Ta,Nb)Fe3Si2O14. These compounds are unique examples of complete chirality (structural chirality and double magnetic chirality [1,2]). They also present magneto-electric effects, which suggest that they are good candidate for multiferroicity and occurrence of electromagnons.On a structural point of view, the studied iron-langasite single crystals are single domain: they are growth with one structural chirality, opposite for the Ta and Nb compound. On a magnetic point of view, the Fe3+ network consists of layers with triangles arranged on a triangular lattice. The helicoidal magnetic structure, observed below TN=27 K, has a periodicity of about 7 times the crystal structure in the stacked direction while the magnetic moments are arranged at 120° in the triangles [1]. Our terahertz measurements revealed two distinct energy ranges for the magnetic excitations with very different and unexpected temperature dependence. The low energy spectra below 15 cm-1 in Ba3TaFe3Si2O14 disappears above TN, while the high energy part remains up to 150K. We have studied these excitations as a function of the sample structural chirality and electromagnetic field polarization.
REFERENCES
1. K. Marty et al PRL 101, 247201 (2008)
2. M. Loire et al PRL 106, 207201 (2011)
Primary author
Sophie de Brion
(Institut Néel, CNRS-UJF)
