Dot size dependence of magnetic properties in microfabricated L10-FePt (001) and L10-FePt (110) dot arrays

L1(0)-FePt (001) and L1(0)-FePt (110) dot arrays with well-defined geometry were fabricated through the use of electron beam lithography and Ar ion etching. The lateral size of dots was varied in the range from 0.2x0.2 to 5x5 mu m(2). Coercivity (H-c) for the perpendicularly magnetized FePt (001) dots increases with decreasing the dot size. In the case of the FePt (110) dots with in-plane magnetization, on the other hand, the dot size dependence of H-c is completely different from that for FePt (001) dots: H-c shows a slight decrease as the dot size decreases. After annealing at 600 degrees C, the values of H-c for both FePt (001) and FePt (110) dots are remarkably enhanced although the dot size dependence shows similar behavior to that before annealing. The magnetization reversal for all the dots occurs through the nucleation of reversed domains and subsequent domain wall propagation. (c) 2006 American Institute of Physics.