Abstract:
The perovskite solid solutions of the type La(2x)Sr(2-2x)Co(2x)Ru(2-2x)O(6) with 0.25 less than or equal to x less than or equal to 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 (50 Oe) 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.
