Theory of Ordered State of Multiparty Freedoms of Atoms and X-Ray Spectroscopy and Scattering

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(1) Orbital States in Perovskite-Type Transition-Metal Oxides and X-Ray Absorption Linear DichroismWe investigated the effect of 3d spin-orbit interaction in V ion in vanadium perovskite-type oxides including LaVO3 and YVO3 on the basis of the perturbation calculation with respect to the V-V Electron transfer and showed that the orbital magnetic moment of V can considerably contribute to the total moment. For YTi03, where in addition the ferromagnetic component in the c-direction, more-than-one kinds of antiferromagnetic modulations are observed in the ab plane, we proposed that a non-collinearity between the spin and orbital moments can explain the more-than-one additional modulations. We furthermore pointed out that the x-ray absorption on linear dichroism signal is to be observed in many perovskites with antihero-orbital orderings, which is in sharp contrast to the absence of x-ray absorption magnetic circular dichroism signal in antiferromagnets.(2) Theory of Antiferromagnetic Ordering in V203V203 is know to exhibit a metal-insulator transition with decreasing the temperature. In the low temperature antiferromagnetic phase, the crystal symmetry changes from the corundum structure in the high temperature phase to the monoclinic one and it shows anomalous magnetic structure reflecting the low symmetry crystal structure. We calculated, by extending the V-ion pair model, the exchange interaction between V-ion pairs and showed that the sign of the exchange interaction is sensitive to the lattice distortion and explain the magnetic ordering without assuming the so far proposed orbital-ordering model.