Effect of ion irradiation on domain nucleation and wall motion in Ni films

Hysteresis and coercivity in ferromagnetic thin films strongly depend on the extent of the domain nucleation and wall motion. Ion irradiation can affect both the number of domain walls existing for a given field history and their mobility. To address these factors, we present a micromagnetic study of magnetisation reversal for non-irradiated and Xe-irradiated 185 nm Ni films at 8.3 K. It is shown that irradiation facilitates reversal domain nucleation and increases the number of pinning centres at least 10-fold, although this does not augment hysteresis. In field magnetic force microscopy (MFM) reveals this to be due to a domain size no larger than the average distance between pinning centres. (c) 2007 Elsevier B.V. All rights reserved.