Magnetic Head Protrusion Profiles and Wear Pattern of Thermal Flying-Height Control Sliders With Different Heater Designs

Abstract

Hard drives featuring sliders with thermal flying-height control (TFC) using thermal expansion of a heating element have been widely used in products for achieving lower magnetic spacing. This approach allows to actively compensate for static FH variations and achieves sub-1-nm clearance during read/write operation. However, the soft-error rate (SER) may not be minimized with an arbitrary heating element due to the nonuniform protrusion profile and the several micrometers of physical separation between reader and writer. Most published work mainly focused on actuation efficiency or reader spacing without detailed study of the relationship between balance of read/write spacing and the location of heating element. This paper uses an established numerical approach with head structure and pole-tip recession profile measured by scanning electron microscope and atomic force microscope to calculate the 3-D protrusion profiles, and to predict the head wear pattern created in TFC stress test, in which an excessive heating power is applied to the heating element so that part of the head is in contact with the spinning disk for a period of time. We also present novel experimental method for measuring wear pattern with angstrom-level resolution by Elastic Peak Maps. TFC sliders with three different heater elements are investigated numerically and experimentally. The numerical results compare well with the measurements in relative wear depths among various layers, and both show that the location and design of heating element have significant effect on the resulting FH profile as well as read and write magnetic spacings. As a result, one can reduce the SER by tailoring the heater design with the considerations of the magnetic requirement and reliability concerns.