Experimental Study on Smear Characteristics Upon Laser Heating in Air and Helium in Heat-Assisted Magnetic Recording

In heat-assisted magnetic recording (HAMR) technology, it is necessary to heat the magnetic layer of disks at a temperature that exceeds the Curie temperature (Tc). When the disk is laser irradiated, the lubricating film and diamond-like carbon (DLC) protective film on the disk surface are heated at high temperatures (300 °C-500 °C). If the lubricant film, DLC thin film, or organic contamination on the disk surface evaporates or thermally decomposes upon laser heating, it adheres as a smear on the slider surface. In view of the negative effect exerted thereof, the solution to this problem is, therefore, critical for the successful application of HAMR. Furthermore, recently developed helium-enclosed hard disk drives are currently utilized in industries. It is, thus, expected that the aforementioned novel HAMR technology will be employed in helium-enclosed drives. In this study, the effects of DLC thin films on the smear characteristics upon the laser heating of disks in air and He are experimentally investigated, and the manner with which these films on the disk surface affects the smear characteristics is clarified. Moreover, the technical countermeasures necessary to reduce the smear with respect to the hydrocarbons from the DLC thin films in HAMR are elucidated and proposed in this article. Simply put, the technical countermeasures depend on the heating temperature, and the use of a mixture of He and air or oxygen gases is found to be effective. This method, however, may not be significantly useful when the heating temperatures exceed 500 °C.