Coupling between Orbital and Lattice Degrees of Freedom in Y_<1-x>Ca_xTiO_3 (0<x≤0.75) : A Resonant X-ray Scattering Study(Condensed Matter : Electronic Structure, Electrical, Magnetic and Optical Properties)

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We have studied the orbitally ordered states in Y_<1-x>Ca_xTiO_3 (0<x≤0.75) by resonant X-ray scattering (RXS) near the Ti K-edge (E〜5 keV) and by powder X-ray diffraction measurements. The RXS intensities at the 1s→4p transition energy (main-edge) gradually decrease with increasing x and remain finite even in the metallic phase for x>0.4. In contrast, the intensities at the 1s→3d transition energy (pre-edge) decrease rapidly with increasing x up to 0.15 and disappear at x〜0.4. The x dependences of the Jahn-Teller distortion is consistent with those of the RXS intensities at pre-edge. Namely, the RXS intensity at the pre-edge energy reflects the orbital ordered state. From our results, we conclude that the magnetic order in Y_<1-x>Ca_xTiO_3 becomes unstable at x〜0.15 when the orbital order is weakened, and the metallic phase appears in x>0.4 when the order of orbitals melts.
社団法人日本物理学会の論文
2005-12-15