Intra-cluster exchange-coupled high-performance permanent magnets

Inert gas condensation has been used to produce Fe-rich Fe–Pt clusters imbedded in C or SiO2. Compositions of the clusters ranged from the single-phase Fe3Pt phase field to the single-phase FePt phase field, and included compositions in the two-phase Fe3Pt+FePt phase field. The as-formed clusters formed in the A1 fcc structure for all compositions, and after proper heat treatment transformed to the Fe3Pt and/or FePt phases, depending on composition. Because the clusters were well isolated, the scale of the phases was limited by the cluster size. This intracluster structuring on such a fine scale ensured that the soft Fe3Pt and hard FePt phases were fully magnetically exchange-coupled with each other, which allowed greater soft phase fractions comparing with previous work. Energy products of the two-phase clusters with 50% Fe3Pt exceeded 25 MGOe, compared to 11.8 MGOe for the single-phase FePt clusters. Micromagnetic simulations revealed remarkable similarities with the experimental results with respect to the relationship between both coercivity and energy product as a function of cluster composition.