CoPt-TiO2 granular-type media with extremely thin Ru intermediate layer were prepared on a highly oriented high-Bs FeCo soft underlayer (SUL) pinned by an IrMn antiferromagnetic layer. Although the increase of the IrMn antiferromagnetic layer thickness deteriorates the crystal orientation of the media, the magnetic properties of the recording layer were little changed. On the other hand, the Hch (Hc in the hard axis direction) of the SUL were greatly decreased and the Hex (exchange coupling field) of the SUL was largely increased. The Hex of about 10 Oe is effective for the magnetic domain control of the SUL. The recording performance was measured by using a SPT head. The S/N increased as the IrMn layer thickness was increased. This improvement of the recording performance seems to be responsible for the magnetic domain control by the IrMn antiferromagnetic layer. Moreover, enough effect was obtained by Hex of about 10 Oe under environment of conventional spin stand measurement system. K Key wor ds : perpendicular magnetic recording, CoPt-TiO2 granular-type media, IrMn antiferromagnetic layer, FeCo soft underlayer. 1 1. I ntro duction Perpendicular magnetic recording systems were proposed about 30 years ago as a method suitable for high-density magnetic recording 1) . At present they are adopted in almost all commercial hard disk drives.Reduction of the film thickness of an intermediate layer between a recording layer and a soft underlayer (SUL) is needed for higher recording densities. Some approaches to reduce the intermediate layer thickness were reported 2)-3) . However, obtained intermediate layer thicknesses were not very thin. So I proposed CoPt-TiO2 media with a highly oriented FeCo SUL with a high-Bs of 2.45 T and a thin Ru intermediate layer 4) . Due to a new designed medium 5)-6) , the minimum Ru intermediate layer thickness for obtaining the squareness ratio (SQ) more than 0.99 was reduced down to 1.6 nm 7) . The oscillatory interlayer magnetic interaction between the recording layer and the SUL was also observed as a function of Ru intermediate layer thickness for the media with such an extremely thin Ru intermediate layer.In the above-mentioned media, the SUL is pinned by an IrMn antiferromagnetic layer. As it is desirable that the IrMn antiferromagnetic layer is thin to increase the crystal orientation of the FeCo layer and to decrease Ru intermediate layer thickness, the IrMn thickness of 4 nm was chosen. However, the pinned effect obtained by such a thin IrMn antiferromagnetic layer is decreased. The exchange coupling field (Hex) measured from the magnetization curve in the easy axis direction was about 10 Oe. I wonder if the oscillatory behavior of the SUL may be caused due to the weak pinned effect and affect the medium noise. So, in this study, the IrMn antiferromagnetic layer thickness was changed, and the relationship between the pinned effect (Hex and magnetic domain) and the recording performance was investigated.
2. E E xperimen tSamples were prepared by using a dc and rf magnetron sputt...
