Modulation in Multiferroic BiFeO₃: Cycloidal, Elliptical or SDW?

Abstract

We present several modulated magnetic ordering models which all describe the high resolution neutron powder diffraction patterns of BiFeO 3 with the same accuracy as the circular cycloid one proposed in [J. Phys. C 15 (1982) 4835]. These orderings are: the elliptical cycloid and the spin density wave (SDW). The ambiguity of the magnetic ordering in BiFeO 3 is important in the context of recent models of the magnetoelectric coupling in perovskites [Phys. Rev. Lett. 95 (2005) 057205 and 96 (2006) 067601].