Spin-glass behaviour of disordered perovskite LaNi1/2Rh1/2O3

The new, potentially ferromagnetic perovskite type oxide LaNi1/2Rh1/2O3 has been synthesized by conventional ceramic techniques. The crystal symmetry is orthorhombic with lattice constants a=5.580(2) A, b=7.846(3) A, c=5.554(2) A in space group Pnma (No. 62). Rietveld refinements on the powder pattern give clear evidence for a disordered B-site occupancy. Magnetic measurements reveal two transitions. In the paramagnetic domain an effective magnetic moment μeff of 1.53(8)μB is accompanied by a Pauli paramagnetic susceptibility of χtip=6.0(3) x 10-4 emu mol-1. Two magnetic transitions are observed, one around 40 K and one at 10 K. The one at ∝40 K is explained by the complete localization of electrons on LS-NiIII whereas the lower one represents the glass temperature of a spin-glass phase. The results imply that the charge distribution is actually not NiII/RhIV, but NiIII/RhIII with Rh thus being diamagnetic. The electrical conductivity and EPR spectra of the compound are presented. (orig.)