Helical bunching and symmetry lowering inducing multiferroicity in Fe langasites

Laura Chaix (1, 2, 3) , Rafik Ballou (1) , Andres Cano (4) , Sylvain Petit (5) , Sophie de Brion (1) , Jacques Ollivier (2) , Louis-Pierre Regnault (6) , Eric Ressouche (6) , Evan Constable (1) , Claire Colin (7) , Joël Balay (8) , Pascal Lejay (8) , Virginie Simonet (1)

1 NEEL - MagSup - Magnétisme et Supraconductivité
2 ILL - Institut Laue-Langevin
3 Stanford Institute for Materials and Energy Sciences
4 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux
5 LLB - UMR 12 - Laboratoire Léon Brillouin
6 MDN - Magnétisme et Diffusion Neutronique
7 NEEL - MRS - Matériaux, Rayonnements, Structure
8 NEEL - CrisMass - Cristaux massifs

In the chiral Ba3(Nb,Ta)Fe3Si2O14 langasites, the triangle-based helical magnetic order is revisited. It follows from the observation by neutron scattering of additional magnetic satellites and gaps in the spin waves spectra. These so-far undetected features are explained by a bunching of the magnetic helices due to single-ion anisotropy, and by a departure of the in-plane magnetic moments from the 120° arrangement due to a structural loss of the 3-fold axis. These weak modulations of the crystallographic and magnetic structures are shown to be responsible for a spin-induced electric polarization in zero and finite magnetic field, thus ascertaining the multiferroicity of these attractive materials.

Mots clés: multiferroic; chirality; neutron scattering

Domaines: Electrons fortement corrélés [cond-mat.str-el]

Laura Chaix, Rafik Ballou, Andres Cano, Sylvain Petit, Sophie de Brion, et al.. Helical bunching and symmetry lowering inducing multiferroicity in Fe langasites. 2015. ⟨hal-01163057v1⟩