DOMAIN-WALL MOTION IN THE PRESENCE OF NUCLEAR SPINS

We investigate the motion of a domain wall in the presence of a dynami cal hyperfine field. At temperature T high compared to the hyperfine c oupling, the nuclear spins create a spatially random potential landsca pe, with dynamics dictated by the nuclear relaxation time T-2. The dis tribution of the domain wall relaxation times (both in the thermal and quantum regimes) can show a long tail, characteristic of stochastic p rocesses where rare events are important. Here, these are due to occas ional strong fluctuations in the nuclear spin polarisation.