Hyperfine fields at ${}^{66}$Ga, ${}^{67,69}$Ge implanted into iron and gadolinium hosts at 6 K, and applications to g-factor measurements

Isomers in ${}^{66}$Ga, ${}^{67}$Ge, and ${}^{69}$Ge were recoil-implanted into ferromagnetic hosts of iron and gadolinium at $\approx 6$~K, and the hyperfine magnetic fields were determined by Time Differential Perturbed Angular Distribution (TDPAD) measurements. The hyperfine field strengths at $\approx 6$~K are compared to the results of previous higher-temperature measurements and the amplitudes of the $R(t)$ functions are compared to empirical expectations. The results show that gadolinium can be a suitable host for high-precision in-beam $g$-factor measurements. The results of new $g$-factor measurements for isomers in ${}^{66}$Ga and ${}^{67}$Ge are $g{(}^{66}$Ga$,7^{-})=+0.126(4)$, supporting a $[{\pi }_{f5\mathrm{/}2}\otimes \nu g_{9\mathrm{/}2}{]}_{7^{-}}$ configuration assignment, and $g{(}^{67}$Ge$,{\frac{9}{2}}^{+})=-0.1932(22)$, derived from a new measurement of the ratio $g{(}^{67}\mathrm{G}\mathrm{e})\mathrm{/}g{(}^{69}\mathrm{G}\mathrm{e})=0.869(9)$. These values are in agreement with previous results. The $R(t)$ amplitudes indicate that the nuclear alignment produced in the isomeric states was significantly lower than the empirically expected $\sigma \mathrm{/}I\approx 0.35$.