Noise characteristics of double-layered perpendicular media using novel soft magnetic underlayer materials

The read/write characteristics of perpendicular media with different soft magnetic underlayer (SMU) materials (Co-Nb-Zr, Co-Ta-Zr, Fe-Ta-C, and Fe-Al-Si), and identical recording layers were investigated using a spin-stand and a merged-type MR head. It was observed that there are strong correlations between the SMU materials and noise characteristics, and found that Co-Ta-Zr and Fe-Ta-C underlayers yield the lowest noise when combined with a Co-Cr-Pt-Ta magnetic recording layer. An advanced medium, made based on those findings, was tested and a maximum D₅₀ of 275 kFCl was observed by using a single pole-type writer and a GMR reader with a shield gap length of 80 nm