Thermodynamics and kinetics during pulsed laser annealing and patterning of FePt films

Abstract

Laser annealing using 25ns pulses of a KrF excimer laser was applied to electrochemical and pulsed laser deposited FePt films of 700nm and 40 or 80nm thicknesses, respectively. The dependence of phase formation and magnetization behavior on the film thickness and the as-deposited state are studied. Models of the film heating are compared to the experimentally observed results. Furthermore a time temperature transformation (TTT) diagram for the ordering of FePt is proposed, summarizing the phase formation in dependence on annealing time and temperature. In agreement with the TTT diagram, laser annealing leads to a disordering of L10-ordered films. By only partially disordering the L10 phase, this approach provides control over the coercivity of hard magnetic FePt films. Local disordering is applied for magnetic patterning of the FePt films with dot patterns in the micrometer size range.