Magnetic Phase Diagrams and Lattice Structure of Nd_<1/2>Ca_<1/2>(Mn_<1-y>M_y)O_3 (M = Ru, Cr and Sc)

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We have derived the magnetic phase diagram for Nd_<1/2>Ca_<1/2>(Mn_<1-y>M_y)O_ (M = Ru, Cr and Sc) based on the neutron powder diffraction measurements. We found that the Ru- and Cr-doping induces an antiferromagnetic-to-ferromagnetic transition at y = 0.01-0.02, while the Sc-doping does not induce the transition up to _y = 0.10. We have found significant dopant dependent effects on the distortion of the MnO_6 octahedra in the heavily-doped region of the long-c phase: the MnO_6 shape approached to the 2-long/4-short type with Ru-doping, while it does to the 4-long/2-short type with Sc-doping. Absence of the ferromagnetic phase in the Sc-doped system can be ascribed to (1) a strong charge-ordering instability due to the 4-long/2-short type distortion of the MnO_6 octahedra and (2) the reduced effective one-electron bandwidth due to the Sc^<3+> (d^0) impurities.
社団法人日本物理学会の論文
2003-04-15