Anomalous hyperfine fields detected with the differential angular correlation method

Time differential perturbed angular distributions of nanosecond-levels of some rare earth nuclei embedded in a ferromagnetic host lattice have been measured. Coulomb excitation with 4–10 MeV α-particles and recoil implantation technique have been used. Some evidences have been found for anomalous hyperfine fields acting on the nucleus in a time period which cannot be resolved. On a time scale starting at about 1 nsec where details can be resolved, the hypothesis of a static hyperfine field parallel to the external polarizing field seems to be justified.