Air bearing and particle simulation of discrete track recording head/disk interfaces

Discrete Track Recording (DTR) belongs to the so-called patterned media technologies. It is believed that with DTR media the maximum storage density can be pushed beyond 500Gbit/in2, by eliminating magnetic transition noise in the radial direction of the disk. It is important to evaluate whether common air bearing simulation and design tools are capable for the development of discrete track recording head/disk interfaces.

Common air bearing simulation tools are based on the numerical solution of the Boltzmann corrected Reynolds equation. Finite element, finite difference or finite volume methods are used for the solution. However, in each finite method the air bearing domain has to be discretized. Fine air bearing features like grooves and ridges in discrete track recording result in large simulation models. To reduce simulation times parallel computing has to be utilized or homogenization techniques have to be applied to the Reynolds equation. However, the Reynolds equation is based on the assumption of a smooth disk surface. Vertical surface structures such as the groove walls in DTR media influence the velocity of particles in the grooves. We used the Direct Simulation Monte Carlo method as applied to the nano channel flow problem in discrete track recording head/disk interfaces to investigate the effect of vertical disk features on slider forces and how manufacturing tolerances result in slider force variations.

Figure 1: Simulation domain for DSMC simulation

Figure 2: Schematic Discrete Track Recording