Spin glassy behavior and large exchange bias effect in cubic perovskite Ba_0.8Sr_0.2FeO_3-δ

A single-phase iron oxide Ba_0.8Sr_0.2FeO_3-δ with a simple cubic perovskite structure in Pm-3m symmetry is successfully synthesized by a solid-state reaction method in O₂ flow. The oxygen content is determined to be about 2.81, indicating the formation of mixed Fe³⁺ and Fe⁴⁺ charge states with a disorder fashion. As a result, the compound shows small-polaron conductivity behavior, as well as spin glassy features arising from the competition between the ferromagnetic interaction and the antiferromagnetic interaction. Moreover, the competing interactions also give rise to a remarkable exchange bias effect in Ba_0.8Sr_0.2FeO_2.81, providing an opportunity to use it in spin devices.