Tunnel window's imprint on dipolar field distributions -: art. no. 097205

We have performed Monte Carlo simulations of interacting dipoles that relax through quantum tunneling. We aim to mimic tunneling experiments on crystals of magnetic clusters, such as Fe(8), at very low temperatures. Accordingly, we allow spin flips only if the corresponding energy change is less than some 2 delta h(hf). Time evolutions of the dipolar field distribution P(t)(H) are studied. As in experiments, a "hole" develops in Pt(H). The half-width III of incipient holes of weakly polarized systems are, under certain conditions, simply related to delta h(hf). For k(B)T less than or similar to 0.5 delta h(hf) and delta h(hf) smaller than approximately 1/10 of the half-width of the dipolar field distributions of disordered systems, W similar or equal to 0.75 delta h(hf).