LAUSR

Abstract Effects of Ru doping on the structure and magnetic properties of La 2 CoMn 1−x Ru x O 6 ceramics with different compositions (x = 0, 0.1, 0.2, 0.3, 0.5, 0.75, 1.0) have been investigated using a variety of complementary techniques (X-ray powder diffraction and photoelectron spectroscopy, electron microscopy, and magnetometry). Phase-pure polycrystalline samples were prepared by the conventional solid-state reaction method including high pressure (3000 kg/cm 2 ) treatment of the original mixture of reagents. X-ray diffraction analyses of the samples accompanied with Rietveld refinement suggested a change in the crystal structure upon doping: for 0 ≤ x ≤ 0.3 the structure of the samples is predominantly disordered orthorhombic (s.g. Pnma ) which transformed to ordered monoclinic (s.g. P2 1 /n ) for 0.5 ≤ x ≤ 1. This suggests that Ru doping induces (partial) cation order in the B- sublattice. Magnetic measurements indicated a low temperature ferromagnetic phase, and a positive value of the Curie–Weiss temperature ( θ cw) was derived for all samples of composition x ≤ 0.75. However, the Curie temperature ( T C ) and θ cw decreased with increasing Ru doping. These changes in T C upon doping can be correlated to the changes in the nearest neighbor and next nearest neighbor exchange interactions. The sample with x = 1 orders antiferromagnetically at approximately 25 K.