Magnetic properties of Sr0.7R0.3CoO3-δ (R = Tb, Er and Ho) perovskites

Abstract

The Sr0.7R0.3CoO3-δ (R = Tb, Ho and Er) perovskite derivatives have been previously studied and described as excellent cathode materials for solid-oxide fuel cells (SOFCs) at intermediate temperatures. They were prepared by soft chemistry procedures involving citrates of the different metal ions, followed by thermal treatments in air, and the crystal structure was characterized from neutron powder diffraction (NPD) data in the 300–1100 K temperature range. In this work, these studies have been accompanied with a low-temperature investigation of the magnetic behavior by NPD, in complement with magnetic measurements. For the three members of the series, NPD data unveils a G-type magnetic structure below TN (∼300 K), with a propagation vector k = 0. There is an antiferromagnetic coupling between the two types of Co atoms, defined in the I4/mmm space group, with the magnetic moments of Co aligned along the c axis of the tetragonal cell. Even at 4 K, the magnetic moments of the rare-earth elements do not participate in the magnetic structure, given their statistical distribution over the Sr positions, and they remain paramagnetic in all the temperature range.