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 (η) and its influence on magnetic properties are investigated. The results demonstrate that the η 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., N₂ or Ar) have little effect on the η 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 O^2-. The SFRO samples annealed at 1100 °C in N₂, exhibiting the highest saturation magnetization (M_S = 2.61 μ_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 °C (ASDs = 10.7%) or 1200 °C (ASDs = 10.95%).

Sleep Health and Road Safety: Continuation of Asia-Pacific Economic Cooperation Sleep Technology Agenda

In 2017, the Asia-Pacific Economic Cooperation Sleep Technology Agenda emphasized the impacts of sleep health on road safety. An official meeting between the Department of Transportation of United States and the International Sleep Science and Technology Association took place in Washington, DC, on February 3, 2020. This was followed by several meetings in Taiwan advocated by the International Sleep Science and Technology Association Taiwan Chapter. We hope to raise the awareness in the government sectors, and to provide the scientific evidence of verified sleep and fatigue-monitoring technologies to avoid numerous tragedies on the road from its root cause.