A Vacancy-Disordered, Oxygen-Deficient Perovskite with Long-Range Magnetic Ordering: Local and Average Structures and Magnetic Properties of Sr2Fe1.5Cr0.5O5

作者：Ramezanipour Farshid; Greedan John E^*; Siewenie Joan; Donaberger Ronald L; Turner Stuart; Botton Gianluigi A

来源：Inorganic Chemistry, 2012, 51(4): 2638-2644.

DOI：10.1021/ic202590r

The local and average crystal structures and magnetic properties of the oxygen-deficient perovskite Sr2Fe1.5Cr0.5O5+y were studied using powder X-ray and neutron diffraction, neutron-pair distribution function analysis, and electron energy-loss spectroscopy. This material crystallizes in the cubic Pm (3) over barm space group, with a = 3.94491(14) angstrom. The oxygen vacancies are distributed randomly throughout the perovskite-type structure, and the average coordination number of the Fe(Cr) sites is S. Refinement of the neutron diffraction data indicates y similar to 0.05. This is in discordance with an earlier report on a material with the same nominal composition and cell constant. Electron energy-loss Cr L-2,L-3-edge spectroscopy shows that Cr3+ is Present, which is also contrary to previous speculation. Neutron-pair distribution function studies show that a brownmillerite-like model involving ordered vacancies and alternating octahedral and tetrahedral coordination at the metal sites, gives a better description of the local structure out to similar to 5 angstrom. A remarkable phenomenon determined by neutron diffraction in Sr2Fe1.5Cr0.5O5 is the occurrence of a long-range G-type antiferromagnetic ordering with T-c approximate to 565 K because cubic oxygen-deficient perovskites with B-site disorder usually do not undergo transitions to magnetically ordered states. The observation of long-range antiferromagnetic order and the T-c value are in accordance with previous Mossbauer spectroscopic studies.

• 出版日期2012-2-20