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

Double-perovskite oxide SrFeReO (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 () and its influence on magnetic properties are investigated. The results demonstrate that the value is well controlled by the annealing temperature, which is as high as 85% when annealing at 1100 °C. However, the annealing atmospheres (e.g., N or Ar) have little effect on the value. At room temperature, the SFRO powders crystallize in a tetragonal crystal structure (space group 4/). 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 Sr, Fe, and Re ions, respectively, and the O element presented as O. The SFRO samples annealed at 1100 °C in N, exhibiting the highest saturation magnetization ( = 2.61 /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 °C (ASDs = 10.7%) or 1200 °C (ASDs = 10.95%).