Structure, magnetic properties, and coercivity mechanism of nanocomposite SmCo5/α-Fe magnets prepared by mechanical milling

Nanocomposite SmCo5+x wt %α-Fe (x=0, 20, 30, and 35) powders were prepared by mechanical milling and subsequent annealing. X-ray analyses show that hard phases can be 1:7, 1:5, or 2:7 phase with the increase of α-Fe content in as-milled powders annealed at 550 °C for 30 min. The high remanence and maximum energy product (BH)max were obtained by this method. The single-phase behavior of some powders was discussed according to the exchange spring model of Kneller and Hawig. For as-milled SmCo5+x wt %α-Fe (x=0, 20, 30, and 35) powders annealed at 550 °C for 30 min, analyses of their initial magnetization curves and the coercivities of minor hysteresis loops in dependence on the applied field reveal that coercivities of these powders are all controlled mainly by domain wall pinning. The addition of α-Fe can not change the coercivity mechanism of powders, although it affects strongly their magnetic properties.