Structure and magnetic properties in the La1−xEuxBaFeCuO5+δ system

The solid solution La1−xEuxBaFeCuO5+δ synthesized in air with 0⩽δ⩽0.13 was studied by X-ray diffraction, 57Fe Mössbauer spectroscopy and susceptibility measurements. Double perovskite with YBaFeCuO5-type structure was observed except for x=0 composition which has a cubic cell. Fe and Cu are generally in square pyramidal environments which differ by their distortion: axially compressed for Fe and elongated for Cu. Mössbauer studies showed the existence of pyramidal Fe3+, Fe3+y and octahedral Fe4+. Electric field gradient calculations allowed to better understand the origin of the distortion of the two pyramidal iron sites.