Chemical order induced by He+ ion irradiation in FePt (001) films

We show that partial chemical ordering can be obtained at moderate processing temperatures by using postgrowth ion bombardment. This was demonstrated both on disordered (S∼0) and partially ordered (S∼0.4) sputtered FePt(001) films in which the order parameter S was increased up to 0.3 and 0.6, respectively. X-ray diffraction measurements indicate that the high crystalline quality of the films is not modified as irradiation proceeds. The changes on the magnetic hysteresis loops are compatible with the expected perpendicular magnetic anisotropy increase. This novel method could have a great impact on the current race toward high anisotropy materials to increase magnetic recording density.