Origin of microscopic surface roughness of perpendicular magnetic flexible disks

Media surface roughness was studied, using spectral analysis (maximum entropy method) to determine the amplitude and wavelength of a single sinusoid that modeled the medium´s surface roughness. The results showed that a smoother surface reduced the head-to-medium spacing and increased the medium´s durability. It was found that the amplitude of the surface roughness changed reversibly with and without externally applied tension. Substrate processing that moves the thermal expansion coefficient and Young´s modulus values closer to those of the metallic layer decreases the surface roughness. It is concluded that surface roughness is caused by microscopic elastic deformation originating from the differences in thermal and mechanical parameters between the metallic layer and substrate