The role of defects in microwave and conventionally synthesized LaCoO3 perovskite

Abstract

In this work we investigate the magnetic, dielectric and charge transport properties of LaCoO3 (LCO) synthesized by two different techniques: microwave assisted and conventionally heated ceramic synthesis. The rapid microwave synthesis conditions are far away from thermodynamic equilibrium and are found to lead to modified crystal defect properties as compared to conventional synthesis. The thermally induced magnetic spin state transition at Ts1 ≈ 80 K is exemplified by temperature (T)-dependent dielectric spectroscopy data, which reveal the appearance of an additional dielectric contribution that is correlated to the transition. Magnetisation, M vs T, and electrical resistivity, ρ vs T, curves show that the additional dielectric phase is strongly influenced by magnetic defects and may be associated with higher spin state clusters in a magnetic spin-state coexistence scenario. We suggest that defects such as oxygen vacancies act as magnetic nucleation centres across the spin state transition Ts1 for the formation of higher spin state clusters in LCO perovskites.