title: Charge, orbital and spin ordering in multiferroic BiMn2O5: density functional theory calculations.
abstract: Charge, orbital, and spin ordering of multiferroic BiMn(2)O(5) are investigated by the full-potential linearized augmented plane-wave (FPLAPW) method as implemented in the WIEN2K package. Both the generalized gradient approximation (GGA) as well as GGA plus the one-site Coulomb interaction (GGA+U) methods are considered for the exchange-correlation energy functional. The obtained results show that BiMn(2)O(5) is found stable in ferrimagnetic state with band gap about 1.23 eV. The results suggest that BiMn(2)O(5) contains two kinds of manganese: the ionicity of Mn1 (Mn(4+)) is +3.6 with magnetic moment of 2.40 μ(B) and the ionicity of Mn2 (Mn(3+)) is +3.4 with magnetic moment of 3.22 μ(B). While charge disproportion between Mn1 and Mn2 is small, the difference between e(g) minority occupancies of Mn(3+) and Mn(4+) cations is large. Both these two properties give direct evidence of charge ordering. The analysis of the Born effective charge reveals that the partial ferroelectric polarization (P(ele)) originates from the charge ordering, which is in agreement with a recent work by Brink and Khomskii [J. Phys.: Condens. Matter, 2008, 20, 434217].
authors.affiliation: School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074, PR China. lineng0724@163.com
authors.forename: Neng
authors.initials: N
authors.lastname: Li
authors.forename: Kailun
authors.initials: K
authors.lastname: Yao
authors.forename: Guoying
authors.initials: G
authors.lastname: Gao
authors.forename: Zhaoyu
authors.initials: Z
authors.lastname: Sun
authors.forename: Liang
authors.initials: L
authors.lastname: Li