Simultaneous metal-insulator and spin-state transitions in Pr0.5Ca0.5CoO3 -: art. no. 052418

Pr0.5Ca0.5CoO3 showed a simultaneous metal-insulator and paramagnetic-paramagnetic spin-state transition of the first-order type at 90 K accompanied by a volume contraction by similar to2%. Neutron diffraction analysis revealed that the volume contraction is mainly attributed to the tilting of CoO6 octahedra which causes a decrease in the Co-O-Co angle. The electron configurations were proposed to be localized t(2g)(6) (trivalent Co) and t(2g)(5) (tetravalent Co) in the low-temperature phase and itinerant t(2g)(5)e(g)(0.5) in the high-temperature phase.