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

Nanocomposite SmCo5+x wt %alpha -Fe (x=0, 20, 30, and 35) powders were prep ared by mechanical milling and subsequent annealing. X-ray analyses show th at hard phases can be 1:7, 1:5, or 2:7 phase with the increase of alpha -Fe content in as-milled powders annealed at 550 degreesC for 30 min. The high remanence and maximum energy product (BH)(max) were obtained by this metho d. 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 %alph a -Fe (x=0, 20, 30, and 35) powders annealed at 550 degreesC for 30 min, an alyses of their initial magnetization curves and the coercivities of minor hysteresis loops in dependence on the applied field reveal that coercivitie s of these powders are all controlled mainly by domain wall pinning. The ad dition of alpha -Fe can not change the coercivity mechanism of powders, alt hough it affects strongly their magnetic properties. (C) 2001 American Inst itute of Physics.