NEUTRON POWDER DIFFRACTION STUDY (T=4.2-300 K) AND POLARIZATION ANALYSIS OF YBACUFEO5+DELTA

The crystal and magnetic structures of the perovskite YBaCuFeO5+delta have been studied in the temperature range T = 4.2-300 K by powder neu tron diffraction. In addition to the antiferromagnetic ordering transi tion at T-N = 442 K, a commensurate-incommensurate magnetic transition is detected at T'(N) = 190 K. Below this temperature, two sets of sat ellite peaks surround the (1/2, 1/2, 1/2) magnetic peak at d similar t o 5.15 Angstrom, collapsing into a single set of satellites below 155 K. Polarization analysis has been performed to confirm the magnetic na ture of the (1/2, 1/2, 1/2)(+/-) satellites.