Low-temperature ordering of FePt thin films by a thin AuCu underlayer

Abstract

We have studied the magnetic and structural properties of AuCu(0–50nm)∕FePt(2–50nm) films after annealing at various temperatures. The results indicate that, by introducing a thin equiatomic AuCu underlayer, the ordering temperature of FePt films with thickness even down to 5 nm can be significantly reduced to 350 °C, at which a large coercivity is developed. In fact, the coercivity is as high as 4.6 kOe for a 5 nm FePt film on a 10 nm AuCu underlayer after annealing at 350 °C and this value is raised up to 7.5 kOe when annealed at 400 °C, while the corresponding sample without a AuCu underlayer has to be annealed at a temperature beyond 600 °C in order to achieve a coercivity of 4 kOe. The ordering of the thin AuCu film at relatively low temperature and thus coherently inducing the ordering of FePt film led to the formation of the ordered FePt phase at a much lowered temperature.