Hyperfine Structure and Nuclear Moments of Gadolinium from Paramagnetic Resonance Spectrum

Abstract

The hyperfine structure in the paramagnetic resonance spectrum of ${\mathrm{Gd}}^{3+}$ was resolved and a nuclear spin of $\frac{3}{2}$ was found for each of the two odd isotopes ${\mathrm{Gd}}^{155}$ and ${\mathrm{Gd}}^{157}$. The ratio of the nuclear magnetic moments is $\frac{{\mu }_I\left({\mathrm{Gd}}^{155}\right)}{{\mu }_I\left({\mathrm{Gd}}^{157}\right)}=0.75\mathrm{}\pm 0.07$. The hyperfine structure in the ${}_{}{}^2{}_{}{}^{}S_{\frac{7}{2}}^{}{}_{}{}^{}$ state of ${\mathrm{Gd}}^{3+}$ arises probably from unpaired $s$-electron states which are admixed to the ground state by configurational interaction. Assuming the same degree of configurational interaction in ${\mathrm{Gd}}^{3+}$ as in isoelectronic ${\mathrm{Eu}}^{2+}$, one finds the ratio $\frac{{\mu }_I\left({\mathrm{Eu}}^{151}\right)}{{\mu }_I\left({\mathrm{Gd}}^{157}\right)}=11.3\mathrm{}$. If one takes ${\mu }_I\left({\mathrm{Eu}}^{151}\right)=3.6\mathrm{}$ nm, the values of the moments of Gd are ${\mu }_I\left({\mathrm{Gd}}^{157}\right)=0.32\mathrm{}$ and ${\mu }_I\left({\mathrm{Gd}}^{155}\right)=0.24\mathrm{}$ nm. The experiments were made on single crystals of La${\mathrm{Cl}}_3$·7${\mathrm{D}}_2$O and ${\mathrm{Bi}}_2$ ${\mathrm{Mg}}_3$ ${\left(\mathrm{N}{\mathrm{O}}_3\right)}_{12}$·24${\mathrm{H}}_2$O using enriched isotopes.