Abstract
Magnetization, resistivity and magnetoresistivity measurements were performed on the bulk samples of Nd 2− x Ce x Cu 1− y M y O 4, where M is Fe, Ni, or Zn. The normal state magnetic susceptibility of Ce doped samples is analyzed by taking into account the crystal field effects on Nd 3+ ions as well as the contribution from Cu 2+ ions. The magnetic susceptibility of Nd 1.85Ce 0.15 Cu 1− y M y O 4 samples followed the Curie-Weiss law between 50 K and 300 K. For Fe and Ni substitutions the magnitude of the effective moments obtained are 2.2μ B and 2μ B respectively. While the former indicates that Fe is in low-spin trivalent state, the latter is found to agree well with the high-spin Ni 2+ in the tetrahedral crystal field as well as low-spin Ni 3+ in the square planar crystal field. For Zn substituted samples the effective magnetic moment remained almost constant about 0.8μ B. This value is associated with the magnetic moment of the Cu 2+ ions. This assignment is consistent with the value of Cu magnetic moment obtained from Fe and Ni substituted samples. The resistivity of all samples in the normal state varied logarithmically with temperature. The observed quadratic dependence of the magnetoresistivity with the applied field signifies the dominance of electron-electron interactions between the conduction electrons.
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