Dual layer overcoat for MR recording media

To achieve high recording areal density, the magnetic spacing loss between the recording head and the disk must be reduced. GMR media require an ultra thin overcoat. Conventional a-C:H and a-C:N media crashed easily as the thickness of overcoat was reduced to less than 75 Å. Ion beam deposited carbon may have better wear resistance but has issues affecting defects and magnetic performance. We have developed a dual layer overcoat for MR and GMR media. With SiN_x as the foundation layer and a-C:H as the top layer of the overcoat, we are able to obtain good tribology performance. The peak position of FTIR spectra of SiN_x films increases from 824.76 to 1140.54 cm^-1 as the ratio of nitrogen to argon increases from 0/80 to 100/80. The binding energy of Si in SiN_x increases from 100.4 eV to 102.2 eV as the nitrogen/argon ratio increases from 20/80 to 100/80. The reduced elastic modulus, E_r, of SiN_x films is a function of flow ratio of argon to nitrogen. E_r value of silicon nitride film can reach 229 GPa for the nitrogen/argon ratio at 20/80