Magnetic phase diagrams and lattice structure of Nd1/2Ca1/2(Mn1-yMy)O3 (M = Ru, Cr and Sc)

We have derived the magnetic phase diagram for Nd1/2Ca1/2(Mn1-yMy)O3 (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 MnO6 octahedra in the heavily-doped region of the long-c phase: the MnO6 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 MnO6 octahedra and (2) the reduced effective one-electron bandwidth due to the Sc3+ (d0) impurities. (author)