Resonant X-ray Study on the Bi-Layered Perovskite Mn Oxide LaSr_2Mn_2O_7

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Charge and orbital ordering behaviors in the halt doped bi-laycred compound LaSr_2Mn_2O_7 have been studied by resonant and non-resonant x-ray scattering. Three different order parameters, which correspond to the A-type aiitiferromagnetism, charge ordering and orbital ordering, were observed by measuring the magnetostriction and the superlattice peaks characterized by wavevectors (1/21/20) and (1/41/40), respectively. The superlattice reflections indicating the charge and orbital ordered states were observed below 210 K. Both the intensities reach a maximum at 160 K on cooling and become very weak below 100K. The peak width of the charge ordered state agrees with that of the orbital ordered state at all temperatures studied. These results indicate that both the states originate from a single phase and that the charge/orbital ordered islands with definite interfaces disperse in the A-typc antiferromagnetic phase. The dimensionality of the charge/orbital ordered phase is discussed using this model.
社団法人日本物理学会の論文
2003-03-15