Giant intrinsic magnetic hardness in RFe5−x Ni x (R=rare earth,x=4 to 5)

Giant low temperature intrinsic magnetic hardness is observed in structurally homogeneous CaCu₅ type compounds RFe_5−x Ni _x . In SmFe_5−x Ni _x , this magnetic hardness peaks approximately at a composition SmFe_0.2Ni_4.8, with an extrapolated coercive force of 230 kOe at absolute zero. The transition metal sublattice is not anisotropic. Thus, the rare earth alone creates giant coercivity. Only compounds withc-axis preference exhibit substantial magnetic hardness (Sm, Er, Tm). Partial substitution of a tetravalent rare earth to produce crystal field anisotropy fluctuations apparently increases coercivity somewhat in the axis-preference compound SmFeNi₄, but has no effect in the plane-preferred compound TbFeNi₄.