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

We show that partial chemical ordering can be obtained at moderate processi ng temperatures by using postgrowth ion bombardment. This was demonstrated both on disordered (S similar to 0) and partially ordered (S similar to 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 p roceeds. The changes on the magnetic hysteresis loops are compatible with t he expected perpendicular magnetic anisotropy increase. This novel method c ould have a great impact on the current race toward high anisotropy materia ls to increase magnetic recording density. (C) 2000 American Institute of P hysics. [S0021-8979(00)45408-3].