Long-aging effects on the properties of La0.5Sr0.5CoO3−δ films

Abstract

The transport and magnetic properties of as-deposited and long-aged La0.5Sr0.5CoO3−δ films prepared by pulsed laser deposition have been investigated. It was found that an oxygen deficiency in the aged film leads not only to a change in the Co3+:Co4+ ratio, but to the formation of a structural disorder in the Co–O–Co conduction channel due to the accumulated oxygen vacancies. In addition to the usual ferromagnetic transition at TC≃250 K, the second magnetic transition was observed at TM≈50 K, which is treated as a freezing of the spin-glass state provided by the weak disorder in the oxygen arrangement.