LASER-INDUCED MICROTEXTURING OF MAGNETIC RECORDING MEDIA

Abstract

The laser texturing experimental system has been established to texture the hard disk substrate surface using a chopped argon ion laser beam. The landing zone of the hard disk substrate surface can be textured successfully with regular topographies, which are critically important to the excellent tribological performance for high magnetic recording density. The precise and flexible control of the system was realized, while it is not available for the mechanical texturing system. The topographies of the textured surfaces were observed by optical microscope and atomic force microscope (AFM). The surface texture was formed with discrete bumps with a spiral distribution. Several types of laser bumps were obtained such as crater, sombrero, dome-like and double-rim crater type. The topographies were investigated in detail under various experimental parameters such as laser incident power, scan speed of the laser beam, laser pulse frequency and laser pulse duration. Considering that the stiction is proportional to the contact area, we tried to reduce and optimize the actual contact area between the head slider and the hard disk surface by reducing the bump size and bump density. The mechanisms responsible for the bump formation were studied so as to understand the processes of the laser - substrate interactions. It is believed that the laser bumps are induced by the capillary effects happened during the heating and cooling processes. The final shapes of the bumps depend on the competition between the thermal capillary effect and the chemical capillary effect. The effects of laser irradiation on the properties of NiP substrate were studied by vibrating sample magnetometer (VSM) for the magnetic properties, and Nanoindenter for the surface hardness. The reliability and durability of the hard disk surface are determined by a series of tribological factors. In attempt to evaluate the tribological behavior of the laser textured hard disk surface, the contact start and stop (CSS) tester was employed to test the stiction, friction and acoustic emission (AE) signal. From the practical point of view, we tried to study the dependence of the stiction and the friction on the bump height and bump distribution so as to find out the optimum surface topographical conditions required for the excellent tribological performance.