Synthesis, structural and physical properties of some rare-earth doped nickel chromites

A systematic investigation of structural, magnetic and transport properties of NiCr_1.9R_0.1O₄ (R = Eu, Dy and Ho) has been undertaken. Rietveld analysis of powder X-ray diffraction data revealed that all the compounds crystallize in the cubic symmetry with Fd₃^m space group having small volume fraction of orthorhombic phase RCrO₃. Both lattice parameter and cell volume decreases with the substitution of heavier rare earth ion which is consistent with the decrease in ionic radius of rare earth ion. The temperature dependent magnetization studies have shown that all our investigated compounds have negative value of Weiss constant. It indicates the dominance of anti-ferromagnetic interactions in the samples. The phases are semi-conductors and the conduction mechanism is dominated by Arrhenius model in the high temperature paramagnetic semiconducting region. (author)