Fabrication of $\hbox {L}1_{2}\hbox {\textendash }\hbox {CrPt}_{3}$ Alloy Films Using Rapid Thermal Annealing for Planar Bit Patterned Media

SiO₂(2 nm)/Cr₂₅Pt₇₅(15 nm) and SiO₂(2 nm)/Cr₂₅Pt₇₅(15 nm)/SiO₂(10, 20 nm)/Co₈₀Zr₁₀Nb₁₀ (10 nm) were prepared by magnetron sputtering method and post-annealed by rapid thermal annealing (RTA) at temperatures of 600°C-1000°C for 1-60 sec. The saturation magnetization M_s and coercivity H_c measured by applying a maximum field of 18 kOe were 150 emu/cc and 12 kOe, respectively, for the sample after rapid thermal annealing at 1000 °C for 30 sec. This means that L1₂-CrPt₃ phase was obtained by RTA process. The RTA process was applied to fabricate the multilayered structure having L1₂-CrPt₃ and CoZrNb soft magnetic underlayer (SUL). The polar Kerr loop of CrPt₃(15 nm)/SiO₂(20 nm)/CoZrNb(10 nm) after RTA at 1000°C for 30 sec exhibited a large coercivity H_c > 9 kOe corresponding to that of the CrPt₃ single layer. From the compositional depth profile of CrPt₃(15 nm)/SiO₂(20 nm)/CoZrNb(10 nm) processed by RTA at 1000°C for 30 sec, sharp layered structure was confirmed despite the high-temperature heat treatment. When the SiO₂ thickness was reduced to 10 nm, such a layered structure was completely destroyed due to the interdiffusion between CrPt₃ and CoZrNb layers. Thus it was concluded that the RTA process and the interlayer of SiO₂ (20 nm) were effective to fabricate layered structure having L1₂-CrPt₃ and SUL.