Structural and magnetic properties of the La2-xCaxCoIrO6 double perovskite series

Abstract

Polycrystalline samples of the series La2-xCaxCoIrO6 (0 <= x <= 1.2) have been synthesized and its structural and magnetic properties were investigated using experiments of X-ray powder diffraction, temperature dependent magnetic susceptibility and magnetization as a function of applied magnetic field. All grown polycrystalline compounds form in a monoclinic structure (space group P2(1)/n) with a partially ordered distribution of transition metal cations Co/Ir over the six-coordinate sites. Our results indicate variation of the magnetic interactions between Co and Ir magnetic sublattices possibly due to valence changes of the transition metals, induced by doping. The undoped La2CoIrO6 presents magnetic ordering at similar to 97 K, while for Ca-doped compounds a decrease of net magnetization and ordering temperatures was observed. For x=0.2 and 0.5 the emergence of a second magnetic interaction, due to the presence of high spin Co3+, becomes evident. Interestingly, for x=0.8 the large effective magnetic moment indicates strong orbital contribution and spin-orbit coupling and/or the presence of Co4+ in high spin state. (C) 2014 Elsevier Inc. All rights reserved.

Polycrystalline samples of the series La2-xCaxCoIrO6 (0 <= x <= 1.2) have been synthesized and its structural and magnetic properties were investigated using experiments of X-ray powder diffraction, temperature dependent magnetic susceptibility and magnetization as a function of applied magnetic field. All grown polycrystalline compounds form in a monoclinic structure (space group P2(1)/n) with a partially ordered distribution of transition metal cations Co/Ir over the six-coordinate sites. Our results indicate variation of the magnetic interactions between Co and Ir magnetic sublattices possibly due to valence changes of the transition metals, induced by doping. The undoped La2CoIrO6 presents magnetic ordering at similar to 97 K, while for Ca-doped compounds a decrease of net magnetization and ordering temperatures was observed. For x=0.2 and 0.5 the emergence of a second magnetic interaction, due to the presence of high spin Co3+, becomes evident. Interestingly, for x=0.8 the large effective magnetic moment indicates strong orbital contribution and spin-orbit coupling and/or the presence of Co4+ in high spin state.