Large hyperfine anomaly between 91Y and 91m Y in Fe

Nuclear magnetic resonance on oriented nuclei was carried out using a sample of dilute Y91 and Y91m in iron prepared by ion implantation of radioactive precursor Rb isotopes. For Y91Fe , the beta-ray asymmetry was utilized to measure the magnetic hyperfine interaction frequency, ν₀=73.566(22)MHz , which led to the magnetic hyperfine field, B_HF=-29.4(2)T , by using the known nuclear g -factor. The field shift of the resonant frequency, dν₀/dB₀=-2.501(17)MHz/T for Y91Fe , implies a Knight shift value, K=0.0(8)% . The interaction frequency and the field shift of Y91mFe obtained via the gamma-ray detection confirmed the previously reported results. A ratio of the measured ν₀ and dν₀/dB₀ values for both Y91Fe and Y91mFe gave rise to the hyperfine anomaly, Δ91m91=-4.2(8)% , which can explain discrepancies in the B_HF values of YFe as determined by various experiments.