Comparative study of ordered and disordered Y_(1-x)Sr_(x)CoO_(3-delta)

摘要

We have succeeded in preparing A-site ordered and disordered Y_(1/4)Sr_(3/4)CoO_(3-delta) with various oxygen deficiencies delta, and have made a comparative study of their structural and physical properties. In the A-site ordered structure, oxygen vacancies order, and (delta)(velence)0.34 sample shows a weak ferromagnetic transition beyond 300 K. On the other hand, in the A-site disordered structure, no oxygen-vacancy ordering is observed, and (delta)(velence)0.16 sample shows a ferromagnetic metallic transition around 150 K. A-site disordering destroys the orderings of oxygen vacancies and orbitals, leading to the strong modification of the electronic phases.