Novel composite perpendicular recording medium with Co78Cr22 over Cr-rich Co72Cr28 for merged MR heads

We propose a new type of composite perpendicular medium consisting of a 50-nm-thick Co₇₈Cr₂₂ upper layer and a 50-nm-thick Cr-rich Co₇₂Cr₂₈ lower layer for magnetic recording systems using MR heads. The lower Cr-rich layer, with strong magnetic interaction in the perpendicular direction and good crystalline orientation, contributes to the high resolution and high signal-to-noise ratio (S/N). The upper layer, with large saturation magnetization (M_s) and large anisotropy field (H_kl), plays a major role in increasing the signal amplitude. Magnetic recording characterization using this medium and a merged MR head yielded a D₅₀ of 140 kFCI, an S/N of 33.4 dB, and a signal amplitude of 411 μV_pp at 100 kFCI with a 62-nm magnetic spacing