Simulation of Thermal Protrusion of Magnetic-head Elements

Abstract

The rapid increase in the recording density of magnetic disk drives has required the flying-height of magnetic head sliders to be decreased to approximately 10nm. However, under such low flying-height conditions, heat due to high-frequency current in the writer coils and rise of the surrounding temperature cause local protrusion of head elements. This protrusion makes the flying-height less than the design value and reduces the safety margin for the head/disk interference. In the current work, heat transfer in the head slider and thermal deformation of the head were numerically simulated. The simulated temperature distribution agrees well with the experimental result measured by infrared microscope. A parameter survey revealed some important design guidelines for making a head that suffers minimum protrusion (that is, a low-protrusion head) : (i) reduction of alumina-basecoat thickness decrease the protrusion; (ii) a silica-alumina-compound cover layer is effective because of its low coefficient of thermal expansion; and (iii) an additional bonding between the trailing end of the slider and the suspension cools the writer coil.