Materials Research Science and Engineering Center


Date of this Version



Published in Mater. Res. Soc. Symp. Proc. Vol. 887. Copyright © 2006 Materials Research Society. Used by permission.


In this paper, we illustrate how to modify the structure and magnetic properties of L10 FePt and PtMn films using ion-beam irradiation. Highly ordered L10 FePt and PtMn phases were achieved directly by using 2 MeV He-ion irradiation without conventional post-annealing. A high ion-beam current density (~μA/cm2 ) was used to achieve direct beam heating on samples. This irradiation-induced heating process provides efficient microscopic energy transfer and creates excess point defects, which significantly enhances the diffusion and promotes the formation of the ordered L10 phase. In-plane coercivity of FePt films greater than 5700 Oe could be obtained after disordered FePt films were irradiated with a He-ion dose of 2.4x1016 ions/cm2. The direct ordering of FePt took place by using ion-irradiation heating at a temperature as low as 230 ℃. In PtMn-based spin valves, an L10 PtMn phase, a large exchange field and a high giant magnetoresistance (GMR) ratio (11%) were simultaneously obtained by using He-ion irradiation. On the other hand, Ge-ion and O-ion irradiation completely destroyed the ferromagnetism of FePt and the GMR of PtMn-based spin valves, respectively.