Limited quenching of the holmium moment by the crystal field in the (Gd,Y)Ni2cubic Laves phase compounds

The hyperfine interaction of ${}_{}{}^{165}{}_{}{}^{}\mathrm{Ho}$ in the cubic Laves phase compounds ${\mathrm{Ho}}_{0.01}{\mathrm{Gd}}_{1-x}{\mathrm{Y}}_x{\mathrm{Ni}}_2$ has been investigated by spin-echo NMR in the composition range $0<x<\mathrm{}0.18\mathrm{}$. In the end compound ($x=0\mathrm{}$) a value of ${9.5}_{\mathrm{\mu }\mathit{B}}$ is obtained for the holmium moment which indicates a 5% quenching by the crystalline electric field. Further quenching takes place with substitution of yttrium for gadolinium. The magnetization anisotropy of these compounds is weak. The substitution of 1-at.% Ho for Gd suffices to rotate the easy axis of magnetization in Gd${\mathrm{Ni}}_2$ from the $〈110〉$ to the $〈100〉$ direction. This direction remains the easy magnetization direction in all compounds studied. The transferred hyperfine interaction is long range and analysis of data indicates considerable participation of the $d$ electrons in the hyperfine interaction in this series.