Impact of High Pressure and High Temperature on Annealed Oxygen-deficient CoSrO3−δ Perovskites: Structural and Magnetization Studies

Abstract

In this brief article, structural, magnetization studies of oxygen deficient perovskite cobalt oxides CoSrO3−δ synthesized in two different ways are reported. The structural refinements (JANA2006) of X-ray powder diffraction data indicate that the sample prepared under ambient pressure (stage-1) shows a hexagonal structure with P63/mmc (194) as a possible space group. The stage-1 sample subsequently sintered at 1450 °C for 1–2 h under high-pressure 6 GPa conditions (stage-2) crystallizes in tetragonal symmetry with I4/mcm (140) space group having a=5.444(7) A and c=7.68(2) A. While the stage-1 sample exhibits a paramagnetic nature in the magnetic susceptibility, M(T), measurements, interestingly the sample annealed under high-pressure conditions shows ferromagnetism in the magnetic susceptibility, M(T) and field dependence magnetization, M(H) measurements. The high-pressure annealed sample shows hysteresis opening with a quite large coercive field of 7.3 kOe at 1.8 K. The temperature dependence of the inverse molar susceptibility curves exhibits linear behavior in the high-temperature regime and could be fitted to the Curie–Weiss expression, χ(T)=C/(T−θW). The experimental values of θW and peff obtained from the linear region of the inverse molar magnetic susceptibility curves are found to be: −210.7(5) K and 2.38(2) μB/Co for stage-1 and 260.2(7) K and 1.87(3) μB/Co for stage-2 samples, respectively. A negative sign of θW indicates rather strong antiferromagnetic correlations in the stage-1 sample. Apart from these results, the structural parameters reported by various groups for the strontium-based perovskite cobalt oxides are also presented in the form of literature collections.