Mechanical and tribological properties of hard carbon coatings for magnetic recording heads

Thin film read-write magnetic heads are commonly used in data processing tape and rigid disk drives. The head body is made of magnetic ferrites or nonmagnetic Al2O3-TiC and the head construction includes coatings of soft magnetic alloys, soft oxides and adhesives. Pole tip/ gap recession (relative wear of the pole tip and gap materials with respect to air bearing surface or ABS) in the inductive head and scratching/ smearing, electrical short, electrostatic charge build up, and corrosion of the MR stripe in the MR heads are major problems. Wear of head structure can be minimized by the application of a wear resistant coating over the entire ABS including the head structure. In this study, we have deposited amorphous carbon by several deposition processes: cathodic are deposition, (direct) ion beam deposition, plasma-enhanced chemical vapor deposition (PECVD), and DC magnetron sputtering and ion beam sputtered Al2O3 and RF sputtered SiC. These coatings were deposited on Ni-Zn ferrite and Al2O3-TiC substrates and were characterized for mechanical and tribological properties. The ion beam carbon coatings on Ni-Zn ferrite and cathodic are carbon coating on Al2O3-TiC exhibited the highest resistance to scratch and wear among all carbon coatings followed by the sputtered SiC coatings on Al2O3-TiC. Hardness and modulus of elasticity were measured for thick coatings. Cathodic are carbon, ion beam carbon, and SiC coatings (400 nm thick) on silicon exhibited hardnesses of about 38, 19, and 27 GPa and elastic moduli of 350, 150, and 240 GPa, respectively. Propensity to produce wear debris were also lowest for cathodic are carbon, and ion beam carbon coatings.