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Heat assisted magnetic recording (HAMR) is a promising hard disk drive technology to reach 4 Tb/in2 storage densities. However, HAMR introduces significant thermal considerations that must be accounted for in air bearing simulations; the laser spot on the recording bit and heat dissipated into the slider by the laser delivery system result in boundary wall temperatures that are several hundred degrees Celsius above ambient. Since the air bearing film between the slider and disk is non-isothermal, the local air properties should be used in the lubrication equation that governs the pressure generation. A molecular gas lubrication equation for the air bearing that accounts for large temperature variation along the film was previously proposed by Fukui and Kaneko, but it has yet to be applied to a HAMR hard disk drive. This paper explains the generalized lubrication equation and also implements it into a realistic 2D simulation using a production slider with approximate HAMR conditions. The minimum flying height increases substantially, while the pitch and roll are inappreciably affected. Thermal creep flow is negligible compared with Poiseuille and Couette flows, and it can be omitted from consideration. The sensitivity of the read/write transducer would be affected by the large increase in minimum flying height; therefore, the thermal flying height control design process must consider these variations due to thermal variations in the air bearing.
Date of Publication: Oct. 2011