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Published in IEEE TRANSACTIONS ON MAGNETICS, VOL. 40, NO. 4, JULY 2004, pp. 2913-2915. Digital Object Identifier 10.1109/TMAG.2004.832118 Used by permission.
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The initial magnetization processes in melt-spun Sm-Co alloys with remanent ratios above 0.7 have been studied. Alloys of (Sm(1/(6+x) Co (5+x)/(6+x) ) 94Nb3C3 (x = 067, 1.7, 2.3 and 3) alloys modified with Nb and C were melt spun at wheel speeds of 20 and 40 m/s, and the compositions span the range between the Sm2Co17 and SmCo5 stoichiometries. Structurally, all alloys formed in the TbCu7-type structure, although a small amount of Sm2Co7 was observed in Sm-rich samples, and a small amount of fcc Co formed in Co-rich samples. From transmission electron microscopy analysis, grain sizes typically ranged from 100 to 500 nm, and the grains were randomly oriented. The as-spun ribbons had remanence ratios of 0.7 and coercivity values ranging from 3 to 18 kOe. The initial magnetization curves showed a steep linear response to the applied field for all samples, suggesting that nucleation-controlled processes dominate the magnetization process. In addition, the initial susceptibility decreased with increasing Sm content, reflecting the anisotropy differences between SmCo5 and Sm2Co17 compounds. The initial susceptibility also increased with increasing wheel speed, suggesting that the microstructure has important ramifications on the magnetization process as well.