Corrosion-resistant protective overcoat for magnetooptical media

Aluminum nitride thin films were prepared by RF reactive magnetron sputtering from an aluminum target in an Ar/N2atmosphere. The composition, structure, and the optical, chemical, and electrochemical properties of AlN films were investigated as a function of sputtering parameters. The ability of AlN overcoats to protect the magnetooptical (MO) TbFe layer was demonstrated by monitoring the Kerr hysteresis loop during an accelerated aging test. No significant change was observed in the MO properties for 30 days of aging at 70 °C and 30% relative humidity (RH). The results indicate that AlN is superior to SiO2as a protective overcoat. Electrochemical corrosion tests were carried out on AlN/TDFe films to examine the corrosion resistance provided by the AlN coating.