Structural and magnetic study of PrBaCo2O5+δ (δ≃0.75) cobaltite -: art. no. 184428

We have investigated the structural and magnetic properties of PrBaCo2O5+delta (deltasimilar or equal to0.75) layered cobaltite. By means of neutron and synchrotron x-ray powder diffraction we have determined the ordered distribution of oxygen vacancies in PrOdelta planes. This order doubles both a and b lattice parameters from the perovskite cell parameter, forming a tetragonal (rather than orthorhombic) structure. On cooling, a paramagnetic to ferromagnetic and an incomplete ferromagnetic to antiferromagnetic transition take place. This second transition leads to a coexistence of ferromagnetic and antiferromagnetic order, forming a canted G-type antiferromagnetic structure. Magnetic data above the ferromagnetic transition evidence a large value of the effective paramagnetic moment of Co, implying that, well below room temperature, Co3+ ions in an octahedral environment present a high-spin state, in contrast to RBaCo2O5.5 cobaltites.