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 deg. 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.