X-Ray Scattering and the Phase Transition of KMnF_3 at 184°K

概要

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The phase transition that KMnF_3 exhibits at T_c=184°K has been studied in detail by X-ray scattering. The anomalous scattering that accompanies the transition near T_c is found to be anisotropic for q∼0.05Å^<-1>. For these wave vectors therefore, the Ornstein-Zernike approximation for the density-density correlation function cannot describe the critical properties. The temperature dependence of the square of the frequency of the soft Γ_<25> mode at R is found to be reasonably well described by a Curie-law divergence. The space group of the condensed phase of KMnF_3 has been reexamined. The space group is found to be the tetragonal I4/mcm(D^<18>_<4h>) rather than the orthorhombic Pbnm (^<18>_<2h>) proposed by Beckman and Knox. The space groups of the condensed phases of KMnF_3 and SrTiO_3 are therefore identical.
社団法人日本物理学会の論文
1970-02-05