Perpendicular magnetic recording disk with ultrathin nucleation film for improved corrosion resistance and method for making the disk
View Patent ↗A perpendicular magnetic recording disk has a granular cobalt alloy recording layer (RL) containing an additive oxide or oxides, an intermediate layer (IL) as an exchange-break layer on the “soft” magnetic underlayer (SUL), and an ultrathin nucleation film (NF) between the IL and the RL. In the method of making the disk, the IL is deposited at a relatively low sputtering pressure, to thereby reduce the roughness of the RL and overcoat (OC), while the NF and RL are deposited at substantially higher sputtering pressures. The resulting disk has good recording properties and improved corrosion resistance over a comparable disk made with an IL deposited at high sputtering pressure and without the NF. The NF may be a discontinuous film with an average thickness of less than about 1 nm.
1. A method for making a perpendicular magnetic recording disk having a substrate; an underlayer of magnetically permeable material on the substrate; a nonmagnetic intermediate layer comprising Ru on the underlayer; a perpendicular magnetic recording layer comprising a granular ferromagnetic Co alloy and one or more oxides of one or more of Si, Ta, Ti and Nb; and a discontinuous nucleation film comprising one or more oxides of an element selected from the group consisting of Ta, Nb, Ti, Si, Mn, and Hf between the intermediate layer and the recording layer, the method comprising:
sputter depositing the Ru-containing intermediate layer at a sputtering pressure less than about 12 mTorr;
sputter depositing the oxide-containing discontinuous nucleation film to an average thickness less than about 1.5 nm on the intermediate layer at a sputtering pressure greater than about 30 mTorr; and
sputter depositing the perpendicular magnetic recording layer on regions of the discontinuous nucleation film and on the Ru-containing intermediate layer not covered by regions of the discontinuous nucleation film.
2. The method of claim 1 wherein sputter depositing the Ru-containing intermediate layer comprises sputter depositing a Ru alloy intermediate layer.
3. The method of claim 1 wherein sputter depositing the oxide-containing nucleation film comprises sputter depositing a film comprising Co, the atomic percent (at.%) of Co in the nucleation film being substantially less than the at.% of Co in the recording layer.
4. The method of claim 1 wherein sputter depositing the oxide-containing nucleation film comprises sputter depositing a film comprising Ru and Ta 2 O 5 , the atomic percent of Ru in the nucleation film being between about 85 and 96.
5. The method of claim 1 further comprising sputter depositing the recording layer on the nucleation film at a sputtering pressure greater than about 30 mTorr.