Structural and physical properties of Re substituted B-site ordered and disordered SrCo1−xRexO3−δ (x=0.1, 0.25, 0.5)

Synthesis conditions, structural, magnetic and transport properties have been studied for SrCo1−xRexO3−δ samples with x=0.1, 0.25, 0.5. SrCo0.9Re0.1O3−δ forms in air and remains stable on cooling indicating that small amounts of Re7+ stabilize a B-site disordered Pm-3m phase inhibiting formation of a hexagonal phase observed for SrCoO3−δ. After oxygenation SrCo0.9Re0.1O2.94 becomes ferromagnetic below 125 K and shows metallic-like conductivity with moderate magnetoresistance at low temperatures. Fully oxygenated double perovskite Sr2CoReO6 (x=0.5) forms under reducing conditions and is tetragonal at room temperature. A hysteretic transition to the antiferromagnetic state at low temperatures (∼50–60 K) is coupled with a drastic change of electronic and thermal properties. Contrary to previous reports [A. Nag et al., Chem. Mater. 20(13) (2008) 4420–4424] SrCo0.75Re0.25O3 is not a partially cation ordered Sr4Co3ReO12 phase, but a mixture of two structural and magnetic phases with disordered SrCo1−xdRexdO3 and ordered SrCo1−xoRexoO3 compositions where xd>0.1 and xo<0.5.