Structural, magnetic, and Mossbauer studies of the PrBaCuFeO5+y compound

We studied the structure and the magnetic properties of the oxygen deficient perovskite PrBaCuFeO5+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-N=380+/-5 K was observed for the y approximate to 0 sample and all the magnetic peaks could be indexed on two propagation vectors k(1)=[1/21/21/2] and k(2)=[1/21/21] from 300 to 2 K. The oxygenated sample y approximate to 0.5 does not display magnetic reflections down to 2 K. The Mossbauer 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 approximate to 0 sample reveal two ferric iron sites (S=5/2) while the oxygenated sample displays an additional iron site with higher valence.