Analysis of giant intrinsic magnetic hardness inSmCo5−xNix

Homogeneous pseudobinary compound series of high magnetic anisotropy exhibit giant intrinsic magnetic hardness at cryogenic temperatures. This work presents data on the temperature and composition dependence of coercive force (${\mathrm{H}}_c$) in $\mathrm{Sm}{\mathrm{Co}}_{5-x}{\mathrm{Ni}}_x$ and $\mathrm{La}{\mathrm{Co}}_{5-x}{\mathrm{Ni}}_x$. The temperature dependence of ${\mathrm{H}}_c$ can be represented quite satisfactorily by a formalism developed by Egami. Saturation moments in $\mathrm{Sm}{\mathrm{Co}}_{5-x}{\mathrm{Ni}}_x$ are shown to be in accord with a model based on local moments, in which moments on Co and Ni ions depend on the number of neighboring Co ions. It is shown, on the basis of this local-moment picture, that the magnitude of $H_c$ at low temperatures in $\mathrm{Sm}{\mathrm{Co}}_{5-x}{\mathrm{Ni}}_x$ is proportional to the number of Co ions weakly exchange-coupled to their surroundings.