Magnetic and transport properties of Nd-Ce-Cu-M-O (M=Fe, Ni, Zn) in the normal state

Magnetization, resistivity and magnetoresistivity measurements were performed on the bulk samples of Nd_2-xCe_xCu_1-yM_yO₄, 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 Nd³⁺ ions as well as the contribution from Cu²⁺ ions. The magnetic susceptibility of Nd_1.85Ce_0.15 Cu_1-yM_yO₄ 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 Ni²⁺ in the tetrahedral crystal field as well as low-spin Ni³⁺ 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 Cu²⁺ 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.