Wear of the magnetic head-carbon overcoated disk interface. A Raman spectroscopy study

Raman spectroscopy was applied in the wear track region of carbon overcoated magnetic storage disks after drag and contact start/stop (CSS) tests with a manganese-zinc ferrite slider. The ratio of the relative intensities of the two major carbon bands, one centred near 1360 cm^-1 (the D band) and the other centred between 1560 cm^-1 and 1580 cm^-1 (the G band) increased with the number of cycles in the drag test and first increased and then decreased in the CSS test. The changed D/G spectral intensity ratio is attributed to temperature changes. Raman spectra of carbon layers sputtered to different thicknesses between 15 nm and 30 nm were essentially identical, indicating uniformity in overcoat composition. Raman spectra are consistent with generally higher temperatures in CSS tests than in drag tests. The intensity of a Raman band centred at 625 cm^-1 increased with number of drag cycles in the slider spectrum. Its frequency and shape corresponds to that reported for manganese ferrite in the literature. Its intensity increase with wear remains to be explained. Laser irradiation of carbon overcoats in a Raman spectrometer can contribute to changes of the carbon structure by heating.