Pole tip recession studies of thin-film rigid disk head sliders I. Mechanisms of pole tip recession growth

Abstract

Pole tip recession (PTR) results in an increase in spacing between recording elements and magnetic media which is undesirable for high magnetic recording. A methodology for an accurate measurement of PTR using an atomic force microscopy (AFM) was developed. A reliable measurement of PTR with AFM consists of: (1) mounting the sample such that air bearing surface (ABS) is as parallel as possible to fast scan direction, (2) selection of fast scan direction along the long axis of a slider and (3) the use of software correction, namely, zero order flatten and first order plane fit, to remove measurement errors. The inductive head sliders with both initially protruded and recessed poles were used for the investigation of the PTR growth as a function of increasing CSS cycles. CSS tests were conducted using laser textured and mechanically textured disks. Based on AFM measurements, microscopy and chemical analyses of the worn sample, mechanisms of PTR growth were proposed. If the poles are protruded, first, the protruded parts of pole tips are knocked off by harder carbon coated laser bumps through adhesive wear and two-body abrasive wear within initial several hundred CSS cycles. Continued contacts at head-disk interface results in the wear of Al 2O 3TiC ABS, Al 2O 3 insulating film, NiFe poles and carbon coated laser bumps which generates abrasive particles. These wear particles result in three-body abrasive wear which selectively removes relatively soft metal poles and leads to a PTR. PTR growth levels off after a certain number of CSS cycles, dependent upon the pole tip design, typical size of wear particles and propensity of stain growth. Formation of stain on the pole tip region is observed after certain number of CSS cycles which minimizes PTR growth, however, stain build up is undesirable.