SrV_0.3Fe_0.7O_2.8: A Vacancy-Ordered Fe-Based Perovskite Exhibiting Room-Temperature Magnetoresistance

We report room-temperature (RT) magnetoresistance (MR) in a novel Fe-based perovskite, SrV_0.3Fe_0.7O_2.8. This compound contains ordered oxygen vacancies in every fifth primitive perovskite (111)_p plane, leading to a layered structure consisting of triple-octahedral and double-tetrahedral layers. Along with the oxygen vacancies, the transition-metal ions are also ordered: the octahedral sites are occupied by 100% of Fe ions, while the tetrahedral sites are occupied by 25% of Fe ions and 75% of V ions. As a result, SrV_0.3Fe_0.7O_2.8 forms a magnetically striped lattice in which the octahedral layers with 100% of magnetic Fe ions are separated by the diluted magnetic layer. The compound exhibits weak ferromagnetism and shows a large negative MR (-5% at 3 T) at RT, despite the small saturation moment (0.4 μ_B/Fe atom). Thus, this type of layered compound is promising for further large MR by an increase of magnetization through chemical substitution.