Compensation for Flying-Height Loss due to Thermal Protrusion of a Magnetic Head: Comparison of Optical Measurement Using an Active Slider with Built-in Thermal Actuator and Numerical Simulation Results

摘要

To achieve an ultralow flying height (FH) in magnetic head sliders for next-generation hard disk drives, we are developing an individual and in-situ technique to adjust FH using a built-in thermal actuator to compensate for FH deviations and variations. We have evaluated changes in the FH of a prototype slider by observing the amplitude of readback signals. However, the observed FH change is much smaller than the predicted value by simulation. To resolve this issue, we evaluated the slider's FH at multiple positions optically, which revealed a "compensation effect" due to increasing air pressure. That is, the pressure on the air-bearing surface increases as the head protrudes downwards by thermal expansion, which lifts the slider upwards. The evaluation also showed a reduction in the pitch angle due to increasing air pressure. These results agree well with FH simulation results that take into consideration thermal expansion on the air-bearing surface.