B-Site Fe/Re Cation-Ordering Control and Its Influence on the Magnetic Properties of Sr2FeReO6 Oxide Powders

Double-perovskite oxide Sr2FeReO6 (SFRO) powders have promising applications in spintronics due to their half-metallicity and high Curie temperature. However, their magnetic properties suffer from the existence of anti-site defects (ASDs). Here, we report on the synthesis of SFRO powders by the sol-gel process. The B-site cationic ordering degree (eta) and its influence on magnetic properties are investigated. The results demonstrate that the eta value is well controlled by the annealing temperature, which is as high as 85% when annealing at 1100 degrees C. However, the annealing atmospheres (e.g., N-2 or Ar) have little effect on the eta value. At room temperature, the SFRO powders crystallize in a tetragonal crystal structure (space group I4/m). They have a relatively uniform morphology and the molar ratios of Sr, Fe, and Re elements are close to 2:1:1. XPS spectra identified that Sr, Fe, and Re elements presented as Sr2+, Fe3+, and Re5+ ions, respectively, and the O element presented as O2-. The SFRO samples annealed at 1100 degrees C in N-2, exhibiting the highest saturation magnetization (M-S = 2.61 mu(B)/f.u. at 2 K), which was ascribed to their smallest ASD content (7.45%) with an anti-phase boundary-like morphology compared to those annealed at 1000 degrees C (ASDs = 10.7%) or 1200 degrees C (ASDs = 10.95%).