First-principles study of structural, electronic, and multiferroic properties in BiCoO3

Abstract

Electronic and magnetic properties of BiCoO(3) have been investigated using the ab initio density-functional calculations with local spin density approximation (LSDA) and LSDA+U methods. The structural stability and the origin of the multiferroism for ferroelectronic and ferromagnetic existence were addressed. It was shown that the stability of the C-type antiferromagnetic (C-AFM) structure is better than that of other possible configurations. The hybridization between Bi-O and Co-O with interplay and a local magnetic moment on the Co(3+) play important roles for the nature of the ferroelectricity and ferromagnetism. Theoretical calculations predict the insulating ground state with a band gap of 2.11 eV in the C-AFM ordering for BiCoO(3) originated from the antiferromagnetic interaction in the ab plane, which is in well agreement with experiments.

Ab initiostudy of the giant ferroelectric distortion and pressure-induced spin-state transition in BiCoO3

“…[16][17][18][19] All the results shown below are obtained with U =6 eV and Hund exchange J=0.9 eV. We note that our test calculations using other reasonable U values, 13,18,19 U =5 and 7 eV, gave qualitatively the same results. The total energies of BiCoO3 (in unit of eV/f.u.)…”

“…Plain GGA [or local-spin-density approximation (LSDA)] calculations 5,6,11,13 seem to qualitatively re- produce the C-type AF and insulating ground state of BiCoO 3 in the ambient phase, which was ascribed to the strong Hund-exchange stabilized HS state of the Co 3+ ions (and thus the AF order and narrow bands) and to the well split-off xy-singlet orbital. However, the band gap of 0.6 eV and the Co 3+ spin moment of 2.4 µ B given by the GGA/LSDA calculations are much smaller than the experimental values of 1.7 eV and 3.2 µ B .…”

Electronic structure, Born effective charges and spontaneous polarization in magnetoelectric gallium ferrite

“…The Kohn-Sham equation [18] was solved using the local spin density approximation (LSDA + U ) [19] with the Hubbard parameter, U = 5 eV, and the exchange interaction, J = 1 eV. LSDA + U has been found to be quite efficient in describing strongly correlated multiferroic systems [20,21] in comparison to the conventional local density approximation (LDA) and generalized gradient approximation (GGA). We employed the simplified, rotationally invariant approach introduced by Dudarev [22].…”

Electronic, magnetic and dielectric properties of multiferroic MnTiO3

“…Many efforts have been devoted to theoretically investigate multiferroic materials over the last decade. [9][10][11][12][13][14][15] It is recognized that ferroelectricity and ferromagnetism are rarely found in the same system because the conventional off-center distortion of the B ion in d 0 state responsible for polar behavior is usually inconsistent with the partially filled d orbitals, which are a prerequisite for a magnetic ground state.…”