Abstract
Abstract The magnetic properties of quaternary oxides Ba3PrM2O9 and Ba3CeM2O9 (M = Ir, Ru) have been investigated. They crystallize in the 6H-perovskite structure with the space group P63/mmc, in which the cation sites with the face-sharing octahedra are occupied by Ir (or Ru) ions, and those within the corner-sharing octahedra are occupied by Pr (or Ce) ions. Magnetic susceptibility measurements for Ba3PrIr2O9 show that an antiferromagnetic interaction between two Ir ions in the Ir2O9 dimer results in a large temperature-independent paramagnetic susceptibility over a wide temperature range. Another interesting result is in the small effective magnetic moments for Ba3PrIr2O9 (0.31(1) μB) and for Ba3PrRu2O9 (0.75(1) μB). The electron paramagnetic resonance (EPR) spectrum of Pr4+ in these compounds was measured by diluting them in the corresponding isomorphous compounds Ba3CeIr2O9 and Ba3CeRu2O9 and lowering the temperature to 4.2 K. A very large hyperfine interaction with the 141Pr nucleus was observed. The results were analyzed based on the weak field approximation. The measured g values are much smaller than |−10/7|, showing that the crystal field effect on the behavior of a 4f electron is large. The low g values correspond to the small effective magnetic moments of the Pr compounds.
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