Mössbauer Study on the Ordered Double Perovskite A₂FeReO₆ (A = Ca, Sr)

Abstract

⁵⁷Fe Mössbauer study on the ordered double perovskite A₂FeReO₆ (A = Ca, Sr) has been conducted. Fe ions are in 2.5+ states that correspond to the hybridized state of 3d t_2g down-spin electrons with Re⁵⁺ 5d t_2g down-spin electrons. The orbital effect due to this seems to be absent. On the metal–insulator transition of Ca₂FeReO₆ specimen, slight change of the electronic state toward Fe³⁺ state is recognized. The quadrupole interaction is well explained by a point charge model, which may suggest that while the electrons of Re are itinerant, those of Fe stay rather localized.