Abstract
The magnetic structures of the perovskites , , and , with rocksalt ordering of the Mn/W ions and layered ordering of Na and the rare-earth ions, have been determined by neutron powder diffraction. The manganese moments in order below 10 K with a propagation vector of and a moment of per ion. The and ions order simultaneously in at 11 K. The resulting magnetic structure is incommensurate with the underlying crystal structure and has the propagation vector of . undergoes two magnetic phase transitions at 15 and 9 K. The structure determined at 11 K is based on two propagation vectors of and . Upon cooling at 6 K the incommensurate vector is no longer present and the moments order only according to . The moments of the Nd and Tb ions are found to remain within the planes of the -site cations, and in the Mn moments also lie within the plane. This study not only reveals magnetic structures with previously unexplored topologies but it also sheds light on the intricate coupling between the two magnetic sublattices.
3 More- Received 13 November 2008
DOI:https://doi.org/10.1103/PhysRevB.79.224428
©2009 American Physical Society