Layered (Cu, Fe) oxides of double perovskite structure: Correlation between structural and magnetic-property changes in upon high-pressure heat treatment

In this paper, we report the correlation between the magnetic property and the local structure in (Formula presented) of the “0112” phase containing an unusually large amount of excess oxygen, δ of (Formula presented) when heat treated under a high pressure of 5 GPa. Magnetic susceptibility measurements showed that upon the high-pressure heat treatment, the lower-temperature magnetic transition which had been observed in normal-pressure synthesized, antiferromagnetic (Formula presented) disappeared and the higher-temperature transition, i.e., the Néel temperature, was lowered. According to a Rietveld analysis based on x-ray-diffraction data and space group (Formula presented) the distinction between Cu and Fe positions along the (Formula presented) axis inside the oxygen pyramid disappeared. Coulometric titrations and Mössbauer spectroscopy measurements strongly suggested the existence of excess oxygen in the yttrium plane.