Origin of soft magnetic nanostructures in an Fe–B binary system revealed by ultra-rapid calorimetry

Abstract Magnetically soft nanostructures have been known to form in a simple Fe–B binary system when ultra-rapid annealing (URA) is employed for processing amorphous precursors. The origin of nano-crystallization induced by URA is of fundamental significance. We have predicted in a previous report (Parsons et al 2018 J. Phys. D: Appl. Phys. 51 415001) that the onset of primary crystallization in amorphous Fe 86 B 14 is increased beyond the glass transition temperature ( T g ) when URA is applied. This could result in accelerated homogeneous nucleation because of the contribution of viscous flow to the nucleation kinetics. However, the direct confirmation of T g in this alloy is yet to be seen experimentally. In this report, we have employed a state-of-the-art Flash DSC and clearly confirmed the glass transition behavior in amorphous Fe 86 B 14 when the heating rate is raised beyond ∼10 3 K s −1 . The direct confirmation of the glass transition under URA conditions highlights the significance of viscous flow in obtaining nano-meter scale microstructures in a simple Fe–B system.