Ferromagnetic-Paramagnetic Patterning of FePtRh Films by Fe Ion Implantation

The crystalline and magnetic properties of 6.12 nm thick Fe_x(Pt_0.68Rh_0.32)_100-x films with 50.0 ≤ x ≤ 64.3 and a potential bit-patterning process that utilizes the FM-PM transition caused by Fe ion implantation were investigated. At room temperature, for 50.0 ≤ x ≤ 55.9 the films were ferromagnetic (FM), with an L1₀ phase, whereas for 57.9 ≤ x ≤ 64.3 the films were paramagnetic (PM), with an phase. This composition dependent FM-PM transition forms the basis of a bit-patterning process in which, at first, micro-fabricated resist masks were prepared on the (ferromagnetic) Fe₅₀ (Pt_0.68 Rh_0.32)₅₀ film. Implantation of Fe ions at a dose of 9 × 10¹⁵ ions/cm² then results in an increase of x in the implanted areas, from 50.0 to 58.3. After annealing, 300 nm FM dots were observed by magnetic force microscopy, which confirmed that only the implanted areas had changed from FM to PM and that the dot areas had remained in the FM phase with the L1₀ structure.