Effect of Humidity on Head Smear Generation in Head-Assisted Magnetic Recording

The causes of head smears deposited on the magnetic head surface due to laser heating in heat-assisted magnetic recording (HAMR) should be investigated to achieve high recording densities of hard disk drives (HDDs). These factors, such as outgassing from components and humidity, also affect smear formation in HDDs. In this study, we focused on the effect of relative humidity (RH) on smears generated via laser heating. Three types of lubricant film [dipped, ultraviolet (UV)-treated, and rinsed] were prepared, and the amount of smear generated on a glass pin surface was evaluated using a pin-on-disk tester with a laser heating system. It was confirmed that the amount of smear increased as the humidity increased, and lubricant films with higher chemical bonding fractions showed less smear generation and lower dependence on humidity. In addition, time-of-flight secondary ion mass spectroscopy (TOF-SIMS) confirmed that the migration of cobalt from the magnetic layer was accelerated by laser heating and humidity.