The effects of A-site cation size disorder in ABO3 type ferromagnetic metallic La0.55Ca0.45MnO3 system have been studied by substituting La3+ and Ca2+ by other ions, while keeping the valency of Mn ions and the A-site cation mean radius <rA> constant in the substituted compounds with different A-site ionic radii variance σ2 = Σi (xiri 2 − <rA>2), where xi and ri are the atomic fraction and ionic radii of i-type ions at A-site, respectively. It is revealed that the A-site disorder induces the decreasing of the magnetization and the increasing of the resistivity. The ferromagnetic Curie point TC decreases with the increasing of the A-site ionic radii variance, too. Moreover, the ground state of the system transits from ferromagnetic metal to glass insulator upon increasing variance of the A-site ionic radii from 0.0003 for La0.55Ca0.45MnO3 to 0.009 for Gd0.55Sr0.45MnO3. It is argued that the suppression of the ferromagnetism is ascribed to the enhanced radial distortion of the MnO6 octahedra due to the increasing A-site disorder.
Study of A-site disorder dependent structural properties and magnetic ordering in polycrystalline perovskite Sm0.5Ca0.5−xSrxMnO3