Adhesive contact modeling for sub-5-nm ultralow flying magnetic storage head-disk interfaces including roughness effects

Abstract

As the slider flying height decreases to sub-5-nm to obtain extremely high-density magnetic recordings of the order of 1Tbit∕in.2, problems of adhesion can cause catastrophic behavior at the magnetic recording head-disk interface (HDI). In the earlier part of the paper, a number of interfacial adhesive models were implemented for simplified HDI configurations (i.e., two flat parallel surfaces and a sphere on a flat surface). With the use of realistic HDI properties, individual adhesive force models, such as van der Waals and electrostatic forces, can provide initial approximations to the adhesive forces present during sub-5-nm flying. In the second part of the paper, realistic roughness conditions applicable to actual HDI’s were modeled using an improved Derjaguin–Muller–Toporov-based elastic-plastic rough surface adhesion model. Specifically, the proposed adhesion model accounts for roughness, the presence of molecularly thin lubricant, and includes electrostatic forces. Using experimentally measured roughness values from ultralow flying HDI’s (root-mean-square roughness of 0.65–1.62 nm), it was found that while the contact force is negligible for an interface with low roughness, the adhesive force dominates such interface. Moreover, the effect of roughness promotes adhesion at higher separations than if a two flat parallel surface configuration is considered. Prior to the onset of contact, the total adhesive force for an interface with low roughness is comparable to a two flat parallel surface approximation. However, the simple flat parallel surface approximation fails to predict the realistic onset of contact due to the exclusion of roughness.