In this study, we address problems of the spike noise from soft magnetic layer by utilizing antiferromagnetic coupling. It was found that magnetic domain structures of soft magnetic layers depend on different materials on the basis of domain observation and that exchange bias field H_<ex> was estimated 40Oe by measuring magnetic fields inside HDDs. Through the experiments using IrMn and PtMn as antiferromagnetic layers, it was concluded the spike nosie from media with greater H_<ex> is reduced more effectively. We obtain satisfactory reduction of the spike nosie and control domain walls of soft magnetic layer by cooling under an application of magnetic field.
