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

We demonstrate that the long-range order parameter S of sputtered FePt (001 ) films may be improved by using postgrowth He ion irradiation. This was de monstrated both on disordered (S similar to 0) and partially ordered (S sim ilar to 0.4) films in which S was increased up to 0.3 and 0.6, respectively . X-ray diffraction analysis showed that these changes are due to irradiati on-induced chemical ordering. The changes in the magnetic hysteresis loops correlate with the expected perpendicular magnetic anisotropy increase. Thi s method may find applications in ultrahigh-density magnetic recording. (C) 2000 American Institute of Physics. [S0003-6951(00)02702-9].