Fe-Co-B/Ni-Fe soft magnetic underlayer with high-saturation magnetization for perpendicular magnetic recording media

Fe-Co-B thin films with a high-saturation magnetization 4/spl pi/M/sub s/ of /spl sim/23 kG were investigated for use as the soft magnetic underlayer in perpendicular magnetic recording media. In order to improve the soft magnetic properties of a Fe-Co-B layer, A Ni-Fe underlayer was examined. The Ni-Fe underlayer was effective in reducing the coercivity H/sub c/ from 43 to 1 Oe and in increasing the in-plane uniaxial magnetic anisotropy, H/sub k/ to /spl sim/330 Oe. In the Fe-Co-B(200 nm)/Ni-Fe(10 nm) double layer, no domain wall was observed. The high H/sub k/ led to a high ferromagnetic resonance frequency f/sub r/ above 3 GHz in the Fe-Co-B/Ni-Fe double layer.