Incommensurate Lattice Distortion in the High Temperature Tetragonal Phase of La_<2-x>(Sr,Ba)_xCuO_4(Condensed matter: electronic structure and electrical, magnetic, and optical properties)

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We report incommensurate diffuse (ICD) scattering appearing in the high-temperature-tetragonal (HIT) phase of La_<2_x>(Sr, Ba)_xCuO_4 with 0.07≤x≤0.20 observed by the neutron diffraction technique. For all compositions, a sharp superlattice peak of the low-temperature-orthorhombic (LTO) structure is replaced by a pair of ICD peaks with the modulation vector parallel to the CuO_6 octahedral tilting direction, that is, the diagonal Cu-Cu direction of the CuO_2 plane, above the LTO-HTT transition temperature T_s. The temperature dependences of the incommensurability δ for all samples scale approximately as T/T_s, while those of the integrated intensity of the ICD peaks scale as (T-T_s)^<-1>. These observations together with absence of ICD peaks in the non-superconducting x=0.05 sample evince a universal incommensurate lattice instability of hole-doped 214 cuprates in the superconducting regime.
社団法人日本物理学会の論文
2006-07-15