The structural, electronic and lattice dielectric properties of multiferroic TbMn2O5 are investigated using density functional theory within the generalized gradient approximation (GGA). We use collinear spin approximations and ignore the spin-orbit coupling. The calculated structural parameters are in excellent agreement with the experiments. We confirm that the ground state structure of TbMn2O5 is of space group Pb21m, allowing polarizations along the b-axis. The spontaneous electric polarization is calculated to be 1187 nC⋅cm−2. The calculated zone-center optical phonons frequencies and the oscillator strengths of IR phonons agree very well with the experimental values. We then derive an effective Hamiltonian to explain the magnetically-induced ferroelectricity in this compound. Our results strongly suggest that the ferroelectricity in TbMn2O5 is driven by the magnetic ordering that breaks the the inversion symmetry, without invoking the spin-orbit coupling.
@article{arxiv.0711.2539,
title = {First-principles study of the lattice and electronic structures of TbMn$_2$O$_5$},
author = {Chenjie Wang and Guang-Can Guo and Lixin He},
journal= {arXiv preprint arXiv:0711.2539},
year = {2009}
}