Structure and magnetic properties of SmxCo5/α-Fe (x=0.65-1.3) prepared by mechanical milling and subsequent annealing

Powder mixtures of SmxCo5 (x = 0.65-1.3) + 20 wt % alpha -Fe were mechanically milled. Annealing these as-milled powders results in the formation of a mixture of the hard phase Sm-(Co, Fe) and the soft phase Fe-Co. For the as-milled Sm1Co5 + 20 wt % alpha -Fe powder, the hard phase changes with the increase of annealing temperatures. The optimal maximum energy product (BH)(max) is obtained in the powder annealed at 550 degreesC for 30 min. Depending on the Sm content in the as-milled SmxCo5 (x = 0.65-1.3) + 20 wt % alpha -Fe powders, the hard phases can be 1:7, 1:5, or 2:7 phase after a heat treatment at 550 degreesC for 30 min. The coercivity of 6.5 kOe and maximum energy product of 17.8 MGOe is achieved for the powder with x = 1.0. The highest coercivity of 9.67 kOe is achieved for the powder with x = 1.2. From the measurements of the coercivity obtained from minor hysteresis loops, it is concluded that the coercivities of this type of magnets are controlled mainly by the domain wall pinning. (C) 2001 American Institute of Physics.