X-ray resonant scattering studies of orbital and charge ordering in Pr 1 − x Ca x MnO 3

摘要: We present the results of a systematic x-ray scattering study charge and orbital ordering in manganite series ${\mathrm{Pr}}_{1\ensuremath{-}x}{\mathrm{Ca}}_{x}{\mathrm{MnO}}_{3}$ with $x=0.25,$ 0.4, 0.5. The temperature dependence at wavevectors, lattice constants, was characterized throughout ordered phase each sample. It found that charge- orbital-order wavevectors are commensurate lattice, striking contrast to electron neutron diffraction studies samples $x=0.5.$ High-momentum-transfer resolution $x=0.4$ 0.5 further revealed while long-range order is present, never established. Above ${T}_{0},$ charge-order fluctuations more highly correlated than fluctuations. This suggests drives these samples. In addition, longitudinal modulation same periodicity as discovered For only observed no indication ordering, nor an additional modulation. also report preliminary investigation loss sample by application magnetic field. Finally, polarization azimuthal compounds both resonant nonresonant limits, compared predictions current theories. qualitatively consistent cluster local density approximation $+U$ calculations electronic structure.