In perpendicular recording, the combination of the single-pole-type (SPT) head and double-layered perpendicular media is very effective to achieve high recording density. For the double-layered media, the spike noise generated from the domain walls of the soft magnetic underlayer (SUL) must be eliminated. It has been reported that applying an antiferromagnetic layer (AFML) is effective to reduce the spike noise due to the pinning of the magnetization of SUL [1], [2]. Authors have reported that the spike noise was completely eliminated by applying AFML underneath the SUL together with using the rapid thermal annealing (RTA) process [3], which is needed to align the magnetization of SUL to the radial direction of the disk.
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