Modification of the structure and magnetic properties of ceramic La2CoMnO6 with Ru doping

Abstract

Effects of Ru doping on the structure and magnetic properties of La2CoMn1−xRuxO6 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/cm2) 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. P21/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 (θcw) was derived for all samples of composition x ≤ 0.75. However, the Curie temperature (TC) and θcw decreased with increasing Ru doping. These changes in TC 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.