HYPERFINE MAGNETIC-FIELDS FOR OS, IR AND PT IN IRON - PREEQUILIBRIUM EFFECTS, DOMAIN ROTATION AND THE AHARONI EFFECT

Hyperfine fields acting on subnanosecond excited states of impurity nu clei recoil-implanted into ferromagnetic hosts are being studied. Thes e measurements are sensitive to effects on the picosecond time-scale t hat accompany implantation as well as to phenomena of longer duration. We review our recent work, mainly on 5d impurities implanted into iro n: which has concerned: (i) the behaviour of the transient field at lo w recoil velocities, (ii) the dependence (magnitude and direction) of the hyperfine field on the applied field, (iii) the site distribution of the implanted nuclei, and (iv) the time the static field takes to r each equilibrium after implantation. It is found that the static hyper fine field takes about 10 ps after implantation to reach equilibrium. Once equilibrium is established the internal fields may be misaligned with respect to the direction of the external field, but this is assoc iated with domain rotation in an incompletely saturated sample rather than with the 'Aharoni effect'.