Effect of Laser Heating Duration on Lubricant Depletion in Heat Assisted Magnetic Recording

Heat assisted magnetic recording (HAMR) is a promising choice to overcome the superparamagnetic limit in magnetic recording to further increase the areal recording density of hard disk drive media. However, HAMR brings about serious problems to slider-disk interface, such as lubricant depletion on disk surface at the high temperature in HAMR. Experimental studies of lubricant depletion under laser irradiation are still very limited so far. It is essential to do experimental studies under real HAMR conditions or under equivalent conditions when a standalone laser is used to emulate HAMR system. Laser heating duration in one heating and cooling process in HAMR is as short as 1 ns. It is believed that lubricant depletion under such short heating duration should be different from that under long time continuous heating. In this work, the effect of laser heating duration in one heating and cooling process on lubricant depletion is studied experimentally on a self-developed HAMR tester. Laser power, laser heating rate and laser heating duration of the tester are tunable and comparable with that of a HAMR head laser. The tester also supports macroscopic study. A method to control laser focus point on disk surface is also developed, which is the prerequisite to control laser heating temperature. From the experimental studies, it is found that longer laser heating duration results in more severe lubricant depletion. It is also found that lubricant depletion under laser heating is caused by both lubricant flow on disk surface and lubricant loss via evaporation/decomposition.

I. Introduction

The areal recording density of hard disk drive has kept increasing for the past decade at a very high rate. The hard disk drive industry is facing a big challenge to overcome the superparamagnetic limit in magnetic recording [1] to further increase the areal recoding density of hard disk drive media. Heat assisted magnetic recording (HAMR) is a promising choice. It uses recording media of very high coercivity, which is too high to be writable for conventional write head. Therefore, a tiny area of the media has to be heated up to a high temperature () with laser to lower the coercivity temporarily before information can be written on the area. However, HAMR brings about serious problems to slider-disk interface, such as lubricant depletion on disk surface at the high temperature in HAMR.