Structure, transport and magnetic properties in La2xSr2−2xCo2xRu2−2xO6

The perovskite solid solutions of the type La2xSr2−2xCo2xRu2−2xO6 with 0.25≤x≤0.75 have been investigated for their structural, magnetic and transport properties. All the compounds crystallize in double perovskite structure. The magnetization measurements indicate a complex magnetic ground state with strong competition between ferromagnetic and antiferromagnetic interactions. Resistivity of the compounds is in confirmation with hopping conduction behaviour though differences are noted especially for x=0.4 and 0.6. Most importantly, low field (50Oe) magnetization measurements display negative magnetization during the zero field cooled cycle. X-ray photoelectron spectroscopy measurements indicate the presence of Co2+/Co3+ and Ru4+/Ru5+ redox couples in all compositions except x=0.5. Presence of magnetic ions like Ru4+ and Co3+ gives rise to additional ferromagnetic (Ru-rich) and antiferromagnetic sublattices and also explains the observed negative magnetization.