Abstract
We have studied the crystal and magnetic structures of the magnetoelectric materials using neutron diffraction as a function of temperature. All three materials display incommensurate antiferromagnetic ordering below , becoming commensurate on further cooling. For , a commensurate-incommensurate transition takes place at low temperatures. The commensurate magnetic structures have been solved and are discussed in terms of competing exchange interactions. The spin configuration within the plane is essentially the same for each system, and the radius of determines the sign of the magnetic exchange between adjacent planes. The inherent magnetic frustration in these materials is lifted by a small lattice distortion, primarily involving shifts of the cations and giving rise to a canted antiferroelectric phase.
3 More- Received 5 January 2005
DOI:https://doi.org/10.1103/PhysRevB.71.214402
©2005 American Physical Society