Anisotropy-graded magnetic media obtained by ion irradiation of L10 FePt

We show that Ar+ irradiation can be used effectively to transform a chemically ordered FePt L10 homogeneous thin film into an anisotropy-graded composite media with tunable magnetic response. This can be exploited to produce magnetic media with high thermal stability and moderate coercivity with potential in high-density magnetic recording applications. The depth distribution of the chemical order parameter, which controls the magnetic switching mechanism of the system, has been determined by high-resolution transmission electron microscopy. The irradiation-induced modifications of the material have been modeled using Monte Carlo simulations for ion transport in solids. The magnetic properties and coupling regimes of the resulting exchange-coupled systems are discussed