Structural, magnetic, and Mössbauer studies of thePrBaCuFeO5+ycompound

Abstract

We studied the structure and the magnetic properties of the oxygen deficient perovskite PrBaCuFeO{sub 5+y} as a function of the removable oxygen y. The average crystal structure was refined from x-ray and neutron powder diffraction data which both confirm the presence of the additional oxygen y in the Pr layer. Long-range three-dimensional (3D) antiferromagnetism with T{sub {sub N}}=380{plus_minus}5 K was observed for the y{approx}0 sample and all the magnetic peaks could be indexed on two propagation vectors {bold k}{sub 1}=[(1)/(2)(1)/(2) (1)/(2)] and {bold k}{sub 2}=[(1)/(2)(1)/(2)1] from 300 to 2 K. The oxygenated sample y{approx}0.5 does not display magnetic reflections down to 2 K. The M{umlt o}ssbauer spectra of this sample display magnetic hyperfine spitting below 70 K which is attributed to spin freezing in random orientations. The hyperfine parameters of the y{approx}0 sample reveal two ferric iron sites (S=5/2) while the oxygenated sample displays an additional iron site with higher valence. {copyright} {ital 1997} {ital The American Physical Society}