Atomic ordering and magnetic properties of polycrystalline L10-FePd dot arrays

The polycrystalline L10-FePd (0 0 1) films considering a highly ordered dot array with various sizes have been successfully prepared by using a microfabrication process. The lateral size of square dots was changed in between 1 and 10 μm. The coercivity (Hc) of patterned L10-ordered FePd films was found to be slightly reduced compared to that of continuous film. Furthermore, Hc was slightly decreased after annealing at 500 °C. In the pinning mechanism, Hc can be determined by strong pinning sites for domain walls, which are the grain boundary regions in L10-ordered polycrystalline FePd films. These results indicate that the dot size dependence of Hc before and after annealing may be related to the pinning mechanism. The long-range ordering parameter (S) was increased after annealing. This demonstrates that post-annealing accelerates L10-FePd ordering, but there is no clear correlation between S and Hc.