Surface and subsurface damages and magnetic recording pattern degradation induced by indentation and scratching

Magnetic recording pattern degradation due to head–disk impact and scratching are simulated by static indentation and scratch testing, respectively, on a pre-recorded thin film magnetic recording disk. Different magnitude of controlled stresses were used to induce stress and physical damage to the magnetic recording disk resulting in erasure and distortion of the magnetic recording pattern. Both nanoindentation and scratching resulted in the elastic–plastic deformation of the multilayer coating of the magnetic recording disk but in different relative magnitude and types of in-plane stresses (which are effective in causing magnetization changes). For residual indentation and scratch depths of the order of the magnetic disk coating thickness, magnetization changes in the recording pattern were observed even though the protective carbon overcoat was not damaged. Large magnetic pattern distortion and erasure results where cracks and pileups, and delamination and buckling damages were observed for deeper indentation marks and scratch grooves, respectively.