Magnetic characterization of the (Zr,Sm)Co_3 phase in Sm(CoFeCuZr)_z magnets

摘要

Magnets with composition Sm(Co_(bal)Fe_(0.2)Cu_(0.1)Zr_x)_8 (x=0;0.02;0.04;0.06,0.08) were studied using x-ray diffraction Rietveld analysis. In addition to the majority 2:17 and 1:5 phases, the magnets present a rhombohedral (SmZr)_1(CoFeCu)_3 (PuNi_3 structure) phase, whose volume fraction increases with Zr addition. Higher Zr contents decrease coercivity and lead to the appearance of impurity phases such as 6:23 (Th_6Mn_(23) structure), 2:7R (Gd_2Co_7 structure), and 5:19R (Ce_5Co_(19) structure) in the magnets. The 1:3R phase was reproduced in a ~(57)Fe-doped sample of Sm_(0.33)Zr_(0.67)Co_3 and its Moessbauer spectra, at several temperatures, were adjusted using four sextets and a nonmagnetic doublet. The beneficial effect of small additions of Zr on the coercivity of the magnets is discussed.