Head–Disk Lubricant Transfer and Deposition During Heat-Assisted Magnetic Recording Write Operations

Lubricant accumulation was found on the media surface the instant when the laser is turned OFF during heat-assisted magnetic recording write operations. By changing the write cycles, laser ON/OFF duration, media, and head temperatures, we find that this lubricant accumulation is related to the change in head-media temperatures. The observed lubricant deposition process is restricted to a short time window (1-2 μs) after the laser is turned OFF. An equilibrium model of thermal displacement due to evaporation and condensation processes is presented and used to discuss the effect of the head-media temperature changes on the lubricant accumulation. Possible solutions to minimize the lubricant transfer and deposition are discussed.

I. Introduction

Heat-assisted magnetic recording (HAMR) is the most promising of the next-generation storage technologies that are currently competing to supplant perpendicular magnetic recording. Recently, HAMR has demonstrated 1 Tb/in² recording density, and the extensibility of HAMR well beyond this areal density seems practical [1]–[3]. HAMR technology enhances the magnetic writing process by the inclusion of a strongly focused optical field that propagates from the read–write head and instantaneously heats the magnetic recording layer to above its Curie temperature, thus allowing magnetic recording on media with ultrahigh magnetic anisotropy that otherwise could not be written with conventional writers. During HAMR writing, the media experiences ultrarapid heating, reaching a peak temperature in excess of 500 °C [4]. These conditions will thermally stress the lubricant film on the media, which, along with the carbon overcoat (COC), protect the magnetic storage layer from environmental, thermal, and tribological degradations. The cumulative effect of these repetitive heating cycles on the redistribution of the lubricant film on the media is a significant concern, due to the need to maintain a functioning lubricant film on the media and the negative effect on the head flyability with lubricant accumulation on its surface. The effect of these high-temperature transients on the distribution of lubricant on the media surface is probed, and specific rates of its accumulation are determined by varying the number of write cycles, laser-ON durations, media temperature, and laser output.