Influence of radiation defects on the hyperfine magnetic field at 181Ta in (Zrsub(0.9)Hfsub(0.1))Fe2

TDPAC measurements for the 133-482 keV γ-ray cascade in 181Ta were performed with 181Hf sources in the ferromagnetic Laves intermetallic compound (Zrsub(0.9)Hfsub(0.1)) Fe2. Two samples, annealed and not annealed after activation of 181Hf in a reactor, were investigated. It was shown that in the annealed sample practically all the 181Ta daughters occupied regular sites in the cubic Zr(Hf) sublattice and experienced a unique magnetic hyperfine field Hsub(h.f.)(Ta) = -6.38 (14) T. In the unannealed source the regular precission was observed only for approx. equal to 50% of 181Ta nuclei, another half of them were located at some 'unobservable' sites due, obviously, to a recoil after the (n, γ) reaction. Possible reasons for discrepancies in the results on Hsub(h.f.). (Ta) reported in the literature are discussed. (orig.)