Study on increasing the coercivity of CoCrPtB media with high Pt content

The dependence of magnetic properties and microstructure on the composition of CrMox (x=0–40 at. %) underlayer and CoCr-based nonmagnetic interlayer has been examined for CoCr18Pt20B4 longitudinal media. In the media using a single CrMo (10 nm) underlayer, the highest coercivity that can be obtained is only 1.9 kOe. The coercivity is drastically increased up to 5.0 and 6.4 kOe by using substrate/Cr (5 nm)/CrMo (5 nm) dual underlayer and substrate/CrMo (10 nm)/CoCr38Mo2 (1.3 nm), respectively. It is clarified that the improvement of the coercivity is mainly due to the enhancement of the quality of the crystal growth of the magnetic layer, which results in the improvement of magnetocrystalline anisotropy field and in-plane crystallographic orientation.