Surface potential and magnetic recording media tribology

A Kelvin probe apparatus was developed to profile surface potential. Measurements were performed on unlubricated and lubricated carbon overcoated thin film magnetic recording media. The surface potential on Perfluoropolyether-lubricated media was more negative than that on the unlubricated carbon overcoat. Sliding, start/stop, and low-flying tests were performed with two-mil sliders, and the surface potential was measured across the test tracks prior to detectable mechanical wear. The surface potential in the test tracks became more negative with the number of cycles during sliding or start/stop, and with decreasing slider-disk spacing during low flying. Degraded lubricants with polar carboxylic acid end groups accumulate and increase the dipole moment in the test tracks.