Quantum corrections in an antiferromagnet: A systematic diagrammatical treatment of the Hubbard model

Coupled spin-orbital fluctuations in a three orbital model for 4dand 5doxides with electron fillingsn3, 4, 5-application to NaOsO3, Ca2RuO4and Sr2IrO4

A unified approach is presented for investigating coupled spin-orbital fluctuations within a realistic three-orbital model for strongly spin-orbit coupled systems with electron fillingsn= 3, 4, 5 in thet_2gsector ofd_yz,d_xz,d_xyorbitals. A generalized fluctuation propagator is constructed which is consistent with the generalized self-consistent Hartree-Fock approximation where all Coulomb interaction contributions involving orbital diagonal and off-diagonal spin and charge condensates are included. Besides the low-energy magnon, intermediate-energy orbiton and spin-orbiton, and high-energy spin-orbit exciton modes, the generalized spectral function also shows other high-energy excitations such as the Hund's coupling induced gapped magnon modes. We relate the characteristic features of the coupled spin-orbital excitations to the complex magnetic behavior resulting from the interplay between electronic bands, spin-orbit coupling, Coulomb interactions, and structural distortion effects, as realized in the compounds NaOsO₃, Ca₂RuO₄, and Sr₂IrO₄.

Spin-charge and spin-orbital coupling effects on spin dynamics in ferromagnetic manganites

Correlation-induced spin-charge and spin-orbital coupling effects on spin dynamics in ferromagnetic manganites are calculated with realistic parameters in order to provide a quantitative comparison with experimental results for spin stiffness, magnon dispersion, magnon damping, anomalous zone-boundary magnon softening and Curie temperature. The role of orbital degeneracy, orbital ordering and orbital correlations on spin dynamics in different doping regimes is highlighted.