First-principles studies of the magnetic structure and exchange interactions in the frustrated multiferroic YMnO3

The electronic structure, magnetism and spin-exchange interactions of a frustrated antiferromagnet YMnO3 have been studied by the density functional theory (DFT) within the generalized gradient approximation (GGA) with the non-collinear magnetic structure calculations performed. The calculations show that triangular spin frustration plays an important role in the formation of bandgap, the decrease in total energy and the inducement of ferroelectric distortion in multiferroic YMnO3. The total energy analyses of the different spin configurations show that the magnetic structure with an intraplane frustrated antiferromagnetic (AFM) coupling between nearest-neighbor Mn spins at the edge sharing triangular network and an interplane AFM spin coupling is preferred. We have also estimated the values of exchange integrals by mapping the calculated total energies onto the Heisenberg spin model. The calculated results are consistent with previous experimental estimations. (C) 2008 Elsevier B.V. All rights reserved.