We have used soft x-ray magnetic diffraction at the Fe3+ L2,3 edges to examine to what extent the Dzyaloshinsky-Moriya interaction in Ba3NbFe3Si2O14 influences its low temperature magnetic structure. A modulated component of the moments along the c-axis is present, adding to the previously proposed helical magnetic configuration of co-planar moments in the a,b-plane. This leads to a helical-butterfly structure and suggests that both the multi-axial in-plane and the uniform out-of-plane Dzyaloshinsky-Moriya vectors are relevant. A non zero orbital magnetic signal is also observed at the oxygen K edge, which reflects the surprisingly strong hybridization between iron 3d and oxygen 2p states, given the nominal spherical symmetry of the Fe3+ half filled shell.
@article{arxiv.1305.1160,
title = {Dzyaloshinsky-Moriya driven helical-butterfly structure in Ba3NbFe3Si2O14},
author = {V. Scagnoli and S. W. Huang and M. Garganourakis and R. A. de Souza and U. Staub and V. Simonet and P. Lejay and R. Ballou},
journal= {arXiv preprint arXiv:1305.1160},
year = {2013}
}