Structural, electrochemical and magnetic characterization of the layered-type PrBa0.5Sr0.5Co2O5+δ perovskite

Abstract

Structural, electrical and magnetic properties of the layered cobaltite PrBa0.5Sr0.5Co2O5+δ have been investigated by means of neutron diffraction, electron diffraction, thermogravimetric analysis and SQUID magnetometry. Rietveld analysis of neutron diffraction data shows the ordered distribution of oxygen vacancies in [PrOδ] planes which doubles the lattice parameters from the simple perovskite cell parameter as a≈2ap and c≈2ap (ap is the cell parameter of the simple Perovskite) yielding tetragonal symmetry in the P4/mmm space group. On heating, above 573K in air, structural rearrangement takes place and the structure can be defined as a≈ap and c≈2ap in the same space group. Oxygen occupancies have been determined as a function of temperature from neutron diffraction results. Initially (≥373K), oxygen occupancy was increased and then decreased with increasing temperature. It was found that at 973K the total oxygen loss is calculated about 0.265 oxygen/formula unit. Oxygen vacancy ordering was observed below 573K, and the oxygen occupancy decreases as cell volume increases with increasing temperature. Area specific resistance (ASR) measurements show a resistance of 0.153Ωcm2 and 0.286Ωcm2 at 973K and 923K, respectively. On cooling, paramagnetic to ferromagnetic and an incomplete ferromagnetic to antiferromagnetic transition takes place. Different behaviours in field cooled and zero-field-cooled measurements leads to a coexistence of ferromagnetic and antiferromagnetic order.