Ion-irradiation-induced direct ordering of L1 FePt phase

Abstract

A highly ordered L10 FePt phase was directly achieved by using 2 MeV He-ion irradiation without conventional postannealing. The coercivity greater than 5700 Oe can be obtained after disordered FePt was irradiated at the beam current of several μA/cm2 with the ion doses of 2.4×1016 ions/cm2. The high beam-current-density results in direct beam heating on samples. In addition, the 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 phase. Consequently, the direct ordering of FePt took place by using ion-irradiation heating at temperature as low as 230 °C. Due to the feasibilities of the fast temperature rise and the focused beam size, this ion-irradiation heating treatment can be potentially used as an alternative technique for the rapid thermal annealing and for the magnetic patterning.