Structural transition from L10 phase to A1 phase in FePt films caused by ion irradiation

The effect of ion irradiation (B+, Cr+, Ga+, and Nb+) on the crystalline structure and magnetic properties of L1(0) (face-centered tetragonal structure) FePt films was investigated. Irradiating with Cr+, Ga+, and Nb+ ions of less than 1 at. % (1.6 x 10(15) ions/cm(2)) dose yielded an almost ideal structural transition from the L1(0) to A1 (face-centered cubic structure) phase withoutdamage to the surface of the film. This structural transition was accompanied by a change in magnetic properties from a hard magnet with a coercivity H-c of similar to 7 kOe to a soft magnet with H-c < 1 kOe. A two-dimensional pattern composed of hard magnetic L1(0) and soft magnetic A1 phases was fabricated by using a focused Ga+ ion beam. (c) 2006 American Institute of Physics.