Surface Energies of Magnetic Recording Head Components

The rate of material removal during fixed abrasive lapping is a function of friction coefficient, the surface tension of the lubricant and of the substrate, and the contact angles between the interfaces. In this study, the authors measured the surface energies of materials typically found in thin film magnetic recording heads using contact angle measurements and the Lifshitz–van der Waals acid/base approach. The different materials tested were Ni_xFe_y, Al₂O₃, and Al₂O₃-TiC. Sample preparation procedures were also considered. The chemical used to wash the surface was observed to affect the measured substrate surface energies. Surface energy values for samples washed with either acetone or hexane showed comparable results. The Ni_xFe_y gave the highest measured surface energy (46.3–48.8 mJ m⁻²) followed by Al₂O₃ (44.1–45.3 mJ m⁻²) and Al₂O₃-TiC (43.3–45.3 mJ m⁻²). In contrast, the oil-washed samples measured generally lower surface energy values. The study characterized the interaction of two lubricant types against the three materials. The oil-based lubricant spreads completely on oil-washed samples mainly because of the low surface tension of the oil (22.0 mJ m⁻²) and did not show measurable contact angles. In comparison, the water-soluble lubricant ethylene glycol, due to its higher surface tension (48.0 mJ m⁻²), formed higher contact angles ranging from 47.2 to 59.6° on the different substrates.