  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 $[\pi_{f5/2} \otimes \nu g_{9/2}]_{7^-}$ configuration
assignment, and $g(^{67}$Ge$,\frac{9}{2}^{+})=-0.1932(22)$, derived from a new
measurement of the ratio $g(^{67}\mathrm{Ge})/g(^{69}\mathrm{Ge}) = 0.869(9)$.
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 $\sigma/I \approx 0.35$.
