We have measured by NMR the hyperfine fields of ${}_{}{}^{89}{}_{}{}^{}\mathrm{Y}$, ${}_{}{}^{59}{}_{}{}^{}\mathrm{Co}$, ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$ in several pseudobinary compounds $\mathrm{Y}{\left({\mathrm{Fe}}_{1-x}{A}_x\right)}_2$ ($A=\mathrm{Co},\mathrm{Al},\mathrm{Pt}$). Well-resolved satellite structures of the Y resonance were observed. This shows that the Y hyperfine field is mainly determined by the interactions with the nearest-magnetic-neighbor atoms. We have analyzed the transferred hyperfine field obtained for various values of $x$ with a view to studying the change with composition of the magnetic moments of the $3d$ atoms in $\mathrm{Y}{\left({\mathrm{Fe}}_{1-x}{\mathrm{Co}}_x\right)}_2$. The magnetic moments for Fe and Co were found to depend differently on $x$. Furthermore, the proportionality between the magnetic moments as derived from magnetization measurements and the hyperfine fields proved not to be fulfilled over the whole concentration range. This is explained as being partly due to a delocalization of the magnetic moments in $\mathrm{Y}{\left({\mathrm{Fe}}_{1-x}{\mathrm{Co}}_x\right)}_2$ with increasing $x$.

• Received 12 January 1976

DOI:https://doi.org/10.1103/PhysRevB.13.4698