Structural, Microstructural and Magnetic Properties of SmCo₅/20wt%Fe Magnetic Nanocomposites Produced by Mechanical Milling in the Presence of CaO

In this work, we demonstrate the possibility of using a soluble ceramic material, 5 wt% CaO, as an additive for an SmCo5/20wt%Fe exchange-coupled nanocomposite obtained by mechanical milling in order to inhibit the grain growth of the soft magnetic phase during annealing, which results in a more stable microstructure and an implicit improvement in the hard–soft interphase exchange coupling. Moreover, we show that the additive improves the phase stability of the composite material, reducing the amount of Sm2Co17-type phases formed during the synthesis process, an important aspect because Sm2Co17 is detrimental to the magnetic performance of the SmCo5/20%Fe nanocomposite. These effects are reflected in a nearly 13% increase in the coercive field (Hc) and a 20% increase in the energy product, (BH)max, for the powders produced using CaO as compared to pure SmCo5/20%Fe nanocomposites processed in the same manner.