A study of GMR read sensor induced by soft ESD using Magnetoresistive Sensitivity Mapping (MSM)
Electrostatic discharge (ESD) can be manifest on giant magnetoresistive (GMR) head either physically (melting of sensor element) or magnetically (degrades in dynamic electrical or quasitest parameters). The latter case is usually suspected as ldquosoftrdquo ESD and known to be a subtle case for study. In this study, we try to differentiate the ldquosoftrdquo ESD from electrical failure, which cause by other means. Ahead with magnetoresistance sensitivity mapping (MSM), which is an additional feature of magnetic force microscope (MFM), the symmetry and sensitivity changes of GMR sensors were further investigated. Advanced analytical tools of atomic force microscope (AFM), MFM and MSM allow unique characterization of head microstructure, and coupled with methodical and systematic failure analysis, may be possible to observe in-situ the previously unknown ESD phenomena unique to GMR head.
Study of shield effect on magnetoresistive head performance using magnetoresistive sensitivity map and spin-stand tester
The effect of the bottom shield on magnetoresistive (MR) head read-back performance was systematically studied by using a spin-stand tester and a magnetic force microscope with magnetoresistive sensitivity map (MSM) capability. Two groups of high density MR heads with identical design, processes and materials, except for their bottom shields, were tested. It was found that the higher the initial permeability of the shield, the smaller the PW50, the steeper the 50% height slope and the smaller the shoulder in the corresponding side of the isolated transition read-back pulse. The MSM images and analysis not only corroborated the spin stand results, but they also gave additional information about the isolated pulse shape and cross-track profile. The MSM was found to be a useful tool in studying the shield effects on isolated pulses as well as their impact on microtrack profiles.
Magnetic imaging by ‘‘force microscopy’’ with 1000 Å resolution
We describe a new method for imaging magnetic fields with 1000 A resolution. The technique is based on using a force microscope to measure the magnetic force between a magnetized tip and the scanned surface. The method shows promise for the high‐resolution mapping of both static and dynamic magnetic fields.