Effect of Co content on magnetic properties of hot-worked Nd-Dy-Ce-Fe-Co-B magnets

The effect of cobalt addition on magnetic properties of hot-worked Nd-Dy-Ce-Fe-Co-B magnets was studied. Ribbons with composition (Nd_11.6Dy₁Ce₁) (Fe_80.4-xCo _x)B₆, where x=0, 2.8, 5.5, 8.4, and 11.2, were prepared by melt spinning. Anisotropic magnets were made by die upsetting at 1073 K with 55.6% reduction in height. The temperature coefficient of Br, α, was improved with increase in cobalt content. Addition of 2.8 at.% cobalt considerably improved the temperature coefficient of Hci, β, compared to the base alloy; however, further additions of cobalt did not improve β. Also, irreversible flux losses showed similar behavior as β. Microstructural investigations showed the existence of a cobalt-rich phase in the 11.2 at.% cobalt specimen. Lower values of β with cobalt-containing specimens may be ascribed to a combination of the changes in the anisotropy field of 2-14-1 phase and their microstructure