Experimental study of smear formation and removal in heat-assisted magnetic recording

Abstract

The head-disk interface (HDI) in heat-assisted magnetic recording (HAMR) hard disk drives is a system where a laser beam is launched from a recording head and focused on a recording disk to facilitate data writing. During the laser exposure, material transfers from the disk to the head surface due to the high temperature field and steep thermal gradient. The material accumulation on the head surface, also known as smear, is a challenging reliability issue for HAMR. In this paper, we experimentally investigated the effect of disk temperature and laser exposure time on the smear formation and studied the smear removal by frictional interactions between the head and the disk. In the experiments, the disk temperature and the laser exposure time were controlled separately to generate the smear, which was later characterized by atomic force microscopy (AFM). The AFM images show that the smear forms when the lubricant evaporation occurs for a certain time, and that the smear amount increases with the disk temperature and the laser exposure time. Furthermore, touchdown experiments were performed using the heads with smear. The results indicate that the smear is mostly removed by friction from the head-disk contact. This study reveals the mechanism of the smear formation in HAMR and presents a mechanical approach to mitigate the smear without damaging the head.