Effects of ball milling duration and sintering temperature on mechanical alloying Fe3Si

Abstract

Fe3Si is under interest as a ferromagnetic electrode of magnetic tunneling junctions (MTJs). Its crystalline structure is important for achieving high device efficiency. This work focuses on mechanical alloying of 3:1 ratio of 99% pure Fe and Si powder mixtures by ball milling and sintering. The mixtures were ball-milled for various durations up to 20 h. Then, they were sintered from 400°C  to 800°C for 4 h in Ar.  SEM images and particle size analysis show significant reduction in average particle size of the mixtures after ball milling for 20 h. The longer duration of ball milling process promotes powder distribution. It results in agglomerated and smooth samples after sintering. XRD analysis indicates that Fe3Si phase appeared after 5 h of mechanical ball milling without sintering. More peaks of Fe3Si phase present at sintering temperatures higher than 600°C, while Fe2Si phase diminishes. However, the amount of Fe2O3 phase increases when sintering at these high temperatures, which strongly affects the magnetic properties of the samples. Magnetic hysteresis loops measured by vibrating-sample magnetometer (VSM) show lower magnetic moments of these samples.  Saturation magnetization of the sample decreases more than 95% when sintered at 800°C, agreeing with high content of Fe2O3.