Ground-state and spin-wave dynamics in brownmillerite SrCoO(2.5)--a combined hybrid functional and LSDA + U study.

We theoretically investigate the ground-state magnetic properties of the brownmillerite phase of SrCoO2.5. Strong correlations between Co d electrons are treated within the local spin density approximations of density functional theory (DFT) with Hubbard U corrections (LSDA+U), and results are compared with those using the Heyd-Scuseria-Ernzerhof (HSE) functional. The parameters computed with a U value of 7.5 eV are found to match closely to those computed within the HSE functional. A G-type antiferromagnetic structure is found to be the most stable one, consistent with experimental observation. By mapping the total energies of different magnetic configurations onto a Heisenberg Hamiltonian, we compute the magnetic exchange interaction parameters, J, between the nearest-neighbor Co atoms. The J values obtained are then used to compute the spin-wave frequencies and inelastic neutron scattering intensities. Among four spin-wave branches, the lowest energy mode was found to have the largest scattering intensity at the magnetic zone center, while the other modes become dominant at different momenta. These predictions can be tested experimentally.