Approach to Magnetic Saturation of Impurities in Iron: Effects on Nuclear Alignment, Perturbed Angular Correlation, Mössbauer, andγ-Ray Thermometry Measurements

Dilute alloys of Mn, Co, Ta, and Ir radioisotopes with iron were cooled to 25 mK; the impurity nuclei were oriented through applied magnetic fields up to $H=15.4\mathrm{}$ kOe. At $H\approx 1$ kOe, sufficient to saturate the iron samples, nonalignments of nuclear hyperfine field with $\overrightarrow{\mathrm{H}}$ of magnitude $\Theta \approx 20°$ were observed with $sin\Theta \stackrel{\sim }{\alpha }\frac{1}{H}$. Errors in perturbed-angular-correlation measured $g$ factors (10-40%), nuclear alignment parameters (10-30%), and ultralow-temperature Mössbauer and $\gamma$-ray thermometry (2 mK) due to insufficient $H$ are discussed.