Nanostructured Mn–Al permanent magnets produced by mechanical milling

Abstract

Prealloyed powders of Mn54Al46 were mechanically milled, and the as-milled powders subsequently annealed at temperatures from 350to600°C to produce the ferromagnetic L10-structured τ phase. It was found that the magnetic properties are strongly dependent on both the fraction of τ phase and the grain size. Due to the nanostructure, a large coercivity, up to 4.8kOe, was obtained for Mn54Al46 powders annealed at 400°C for 10min. Both remanence curves and δM plots showed no exchange coupling between the τ-phase nanograins. The mechanism for the magnetization process was determined to be domain-wall pinning type.