The magnetic ordering of the hexagonal multiferroic compound YbMnO3 has been studied between 100 K and 1.5 K by combining neutron powder diffraction, 170Yb M\"ossbauer spectroscopy and magnetization measurements. The Yb moments of the two crystallographic sites order at two different temperatures, the 4b site together with the Mn moments (at TN≃85 K) and the 2a site well below (at 3.5 K). The temperature dependences of the Mn and Yb moments are explained within a molecular field model, showing that the 4b and 2a sites order via Yb-Mn and Yb-Yb interactions respectively. A simple picture taking into account the local Mn environment of the Rare earth R (4b) ion is proposed to couple R and Mn orders in hexagonal RMnO3 manganites. The nature and symmetry of the R-Mn interactions yielding the R order are discussed.
@article{arxiv.0809.5013,
title = {Magnetic order in YbMnO$_3$ studied by Neutron Diffraction and M\"ossbauer Spectroscopy},
author = {X. Fabrèges and I. Mirebeau and P. Bonville and S. Petit and G. Lebras-Jasmin and A. Forget and G. André and S. Pailhès},
journal= {arXiv preprint arXiv:0809.5013},
year = {2008}
}