Orbital and charge orderings and magnetism in perovskite-type transition-metal oxides

The electronic, magnetic and structural properties of prototypical systems where orbital ordering plays important roles are studied by first-principles calculations. The following three materials will be treated: LaMnO3, YVO3 and La0.5Sr1.5MnO4. We demonstrate that there is some qualitative difference in the dominant source for the orbital ordering among these three systems. The present study also suggests that the main difference between the nominal Mn3+ and Mn4+ in La0.5Sr1.5Mno4 is attributed to the difference in the orbital polarization rather than in the charge state.