Flying height control sliders with piezoelectric and thermal nanoactuators for ultrahigh density magnetic recording

The central theme of this dissertation is a comparative study of flying height (FH) control sliders with piezoelectric and thermal actuation as well as a comprehensive study of the design, fabrication, modeling and dynamic control of the piezoelectric nanoactuator for achieving a FH of ∼2 nm, which is required for an area data density of 1 Tbit/in 2, which is the goal on the next generation of hard disk drives.;It is found that the intermolecular and electrostatic forces at the head-disk interface that occur at such small spacing are effectively reduced in both approaches. The thermal protrusion of FH control sliders can be controlled by adjusting the power of the heating elements, but the inherent power-consuming thermal actuation limits the actuation displacement, especially for battery powered mobile applications. The quasi-static nature allows thermal FH control sliders to compensate the static spacing loss. The piezoelectric dynamic control slider shows promising performance of higher bandwidth, larger actuation displacement, and higher power efficiency. However, the requirement of piezoelectric materials and the modification of the slider design pose challenges for the fabrication process and increase the manufacturing cost.;Even though the protruded area was relatively small for a thermally actuated slider, there was still considerable counter effect of the air bearing, resulting in an actuation efficiency of only ∼50%. A new air bearing surface (ABS) design, called "Scorpion III", is presented, which demonstrates an overall enhancement, including virtually 100 percent efficiency with significantly less power consumption.;Another ABS design, named "Scorpion IV", was designed and fabricated for a piezoelectric slider. Dynamic analysis by numerical simulations show that Scorpion IV exhibits an overall enhancement in flying performance, such as track-seeking and dynamic load/unload, due to its remarkably high stiffness and damping. We also propose an inexpensive and low-temperature process for integrating the piezoelectric material in the fabrication of current Al 2O3-TiC sliders, and we conducted experimental analysis to investigate the flying and actuation performances of the fabricated head-gimbal-assemblies. The FH was successfully reduced from about 10 nm to contact, and a track of considerable lube depletion and carbon wear was observed after the contact tests.;To dynamically suppress the FH modulation (FHM) under intermolecular and electrostatic forces for the actuated air bearing slider we present a new 3-DOF analytic model of an observer-based nonlinear compensator for calculating the required control voltage for the piezoelectric nanoactuator. The nonlinear air bearing stiffness and damping were identified by impulse responses, and these values were used in the model. Numerical simulations show that the response of the model is in good agreement with a Dynamic Simulator developed in the Computer Mechanics Laboratory. However, the model requires much less computation time, and hence it can be used as a plant for the observer-based nonlinear sliding mode controller. Numerical studies show that the FHM due to disk waviness was effectively controlled and reduced.;The key contributions of this dissertation are the identification of some of the mechanical challenges inherent in ultrahigh density magnetic recording required for the next generation of hard disk drives as well as some solutions to address these challenges.