抄録
The relation between structures and electromagnetic properties is reviewed on vanadium oxides with the trellis lattice and the A-site ordered perovskite manganites. These compounds show novel phase transitions in which the charge, orbital and spin degrees of freedom are coupled with the lattices. For example, a quarter filled ladder system α'-NaV2O5 undergoes a charge order transition at 35 K, accompanied by lattice dimerization and spin gap formation, and under high pressure it shows various stacking sequences of the zigzag-type in-plane charge-order along the c-axis, so-called “Devils Flowers”. On the other hand, the novel properties of the A-site ordered perovskite manganites are closely related to the most remarkable structural property that the MnO2 layer is sandwiched by two types of rock salt layers with very different lattice sizes.
