Effect of Cr100−xTix (x = 0–19 at.%) alloy underlayers on the high coercivity of FePt thin film below the substrate temperature of 250 °C

The effect of Cr100−xTix underlayer on orderd-L10 FePt films was investigated. A low-temperature ordering of FePt films could be attained through changing the Ti content of Cr100−xTix underlayer. The ordering temperature of the 30 nm FePt film grown on 20 nm Cr90Ti10 underlayer was reduced to 250 °C which is practical manufacture process temperature. An in-plane coercivity was very high to 6000 Oe and a ratio of remnant magnetization (Mr) to saturation magnetization (Ms) was as large as 0.85. This result indicates that the coercivity obtained at 250 °C by the effect of CrTi underlayer is significantly higher than those obtained at 250–275 °C by the effect of underlayers in other conventional studies. The prominent improvement of the magnetic properties of ordered FePt thin films at low temperature of 250 °C could be understood with considering the strain-induced ordering phase transformation associated with lattice mismatch between Cr underlayer and FePt magnetic layer due to an addition of Ti content.