First-principles study on the electronic structure and magnetism of layered oxyselenide La2Mn2Se2O3

The electronic structure and magnetism of layered oxyselenide La(2)Mn(2)Se(2)O(3) have been studied by using first-principles calculations within the generalized gradient approximation (GGA) and GGA + U methods. The G-type antiferromagnetic (AF) state is calculated to be the most stable phase among the various magnetic configurations of interest, irrespective of the choice of the functional used, which is in good agreement with the experiments. In contrast to La(2)Fe(2)Se(2)O(3) and La(2)Co(2)Se(2)O(3), in which the AF states show metallic behavior under the GGA method, we predict the ground state of La(2)Mn(2)Se(2)O(3) is a semiconductor with an indirect band gap of ～0.52 eV via the GGA calculations. This is closely related to a closed shell configuration and large exchange splitting (～3.5 eV) in the Mn 3d states. Moreover, the magnetic properties are also discussed in terms of the calculated Heisenberg spin exchange constants, suggesting that La(2)Mn(2)Se(2)O(3) is a strong two-dimensional magnetically frustrated system.