Magnetic ground state and multiferroicity in BiMnO3
I. V. Solovyev+*, Z. V. Pchelkina* 1)
+Computational Materials Science Center, National Institute for Materials Science, Tsukuba, Ibaraki 305-0047, Japan
*Institute of Metal Physics Ural Division RAS, 620041 Yekaterinburg GSP-170, Russia
PACS: 71.10.Fd, 75.25.+z, 75.30.-m, 77.80.-e
Abstract
We argue that the centrosymmetric C2/c symmetry in BiMnO3 is
spontaneously broken by antiferromagnetic (AFM) interactions existing
in the system. The true symmetry is expected to be Cc,
which is
compatible with the noncollinear
magnetic ground state, where the ferromagnetic order along one
crystallographic axis coexists with the hidden AFM order and
related to it ferroelectric polarization along two other axes. The C2/c
symmetry can be restored by the magnetic field T, which
switches off the ferroelectric polarization. Our analysis is based on the
solution of the
low-energy model constructed for the 3d-bands of BiMnO3,
where all the parameters have been derived from the first-principles
calculations. Test calculations for
isostructural BiCrO3 reveal an excellent agreement with
experimental data.