Related papers: LaVO$_3$: a true Kugel-Khomskii system
The electronic structure of the perovskite LaCoO$_3$ for different spin states of Co ions was calculated in the LDA+U approach. The ground state was found to be a nonmagnetic insulator with Co ions in a low-spin state. Somewhat higher in…
It is shown that the time-reversal symmetry is broken during the phase transition causing orbital ordering in a crystal with Jahn-Teller (J-T) ions. This means that such phase transitions are magnetic ones. As an example we have considered…
The single layered manganite Pr$_{0.22}$Sr$_{1.78}$MnO$_4$ undergoes structural transition from high temperature tetragonal phase to low temperature orthorhombic phase below room temperature. The orthorhombic phase was reported to have two…
We summarize some characteristic features of the frustrated magnetic interactions in spin-orbital models adequate for cubic transition metal oxides with orbital degeneracy. A generic tendency towards dimerization, found already in the…
Ruthenium-based perovskite systems are attractive because their Structural, electronic and magnetic properties can be systematically engineered. SrRuO$_3$/SrTiO$_3$ superlattice, with its period consisting of one unit cell each, is very…
We use ab initio electronic structure calculations within the generalized gradient approximation (GGA+U) to density functional theory (DFT) to determine the microscopic exchange interactions in the series of orthorhombic rare-earth…
The effective Hamiltonian for perovskite titanates is derived by taking into account the three-fold degeneracy of $t_{2g}$ orbitals and the strong electron-electron interactions. The magnetic and orbital ordered phases are studied in the…
We present magnetization and magnetostriction studies of the insulating perovskite LaCoO3 in magnetic fields approaching 100 T. In marked contrast with expectations from single-ion models, the data reveal two distinct first-order spin…
Orbital and spin ordering phenomena in strongly correlated systems are commonly studied using the local-density approximation + dynamical mean-field theory approach. Typically, however, such simulations are restricted to simplified models…
In the series of 3d1 t2g perovskites, SrVO3--CaVO3--LaTiO3--YTiO3 the transition-metal d electron becomes increasingly localized and undergoes a Mott transition between CaVO3 and LaTiO3. By defining a low-energy Hubbard Hamiltonian in the…
A hypothetical layered oxide La_2NiMO_6 where NiO_2 and MO_2 planes alternate along the c-axis of ABO_3 perovskite lattice is considered theoretically. Here, M denotes a trivalent cation Al, Ga,... such that MO_2 planes are insulating and…
A detailed high-resolution, variable temperature powder diffraction study of the fluoro-perovskites NaFeF$_3$ and NaCoF$_3$ is performed to probe their orbital ordering transitions. Through analysis of the symmetry adapted macrostrains and…
Using the formalism of pseudospin and isospin operators the Hamiltonian of an effective Kugel-Khomskii model with spin-orbit coupling is derived with an exact account of the $t_{2g}$ multiplet splitting by the crystal field. An analytical…
The model developed for LaMnO$_3$ addresses the spin-orbital order by superexchange and Jahn-Teller orbital interactions in the cubic (perovskite) symmetry up to now whereas real crystal structure is strongly deformed. We identify and…
Spin reorientation and magnetisation reversal are two important features of the rare-earth orthorhombic provskites ($RM$O$_{3}$'s) that have attracted a lot of attention, though their exact microscopic origin has eluded researchers. Here,…
The origin of successive phase transitions observed in the layered perovskite $\alpha$-Sr$_2$CrO$_4$ is studied by the density-functional-theory-based electronic structure calculation and mean-field analysis of the proposed low-energy…
Perovskite oxides are known to exhibit many magnetic, electronic and structural phases as function of doping and temperature. These materials are theoretically frequently investigated by the DFT+U method, typically in their ground state…
The Kugel-Khomskii Hamiltonian for cubic titanates describes spin and orbital superexchange interactions between $d^1$ ions having three-fold degenerate $t_{2g}$ orbitals. Since orbitals do not couple along "inactive" axes, perpendicular to…
Magnetization measurements of LaCoO$_{3}$ have been carried out up to 133 T generated with a destructive pulse magnet at a wide temperature range from 2 to 120 K. A novel magnetic transition was found at $B>100$ T and $T>T^{*}=32\pm 5$ K…
The perovskite oxide EuTiO3 (ETO) has attracted increased scientific interest due to its potential multiferroic properties and magnetic activity above and below its structural phase transition at TS=282K. Various experiments have indirectly…