The effect of Cu-doping on the magnetic and transport properties of   La0.7Sr0.3MnO3
  The effects of Cu-doping on the structural, magnetic, and transport properties of La0.7Sr0.3Mn1-xCuxO3 (0 < x < 0.20) have been studied using neutron diffraction, magnetization and magnetoresistance (MR) measurements. All samples show the rhombohedral structure with the R3c space-group from 10K to room temperature (RT). Neutron diffraction data suggest that some of the Cu ions have a Cu3+ state in these compounds. The substitution of Mn by Cu affects the Mn-O bond length and Mn-O-Mn bond angle resulting from the minimization of the distortion of the MnO6 octahedron. Resistivity measurements show that a metal to insulator transition occurs for the x more than 0.15 samples. The x = 0.15 sample shows the highest MR(_80%), which might result from the co-existence of Cu3+/Cu2+ and the dilution effect of Cu-doping on the double exchange interaction. 
M. S. Kim (1,2), J. B. Yang (1,2) Q. Cai (4), X. D. Zhou (2), W. J.   James (2,3), W. B. Yelon (2,3), P. E. Parris (1), D. B...