Measuring and specifying limits on current transients and understanding their relationship to MR head damage

In recent years, there has been a tremendous effort in the disk drive industry to produce devices with greater storage capacity and better performance. This push for increased density has led the industry to rely more and more exclusively on magnetoresistive (MR) or giant magnetoresistive (GMR) heads in drive design. These heads have significant advantages over the older inductive heads and have helped to increase area densities to new heights. Unfortunately, these devices are extremely sensitive to damage from current transients. Consequently, manufacturers of heads and disk drives have established specifications for all aspects of handling and testing of heads. These guidelines are designed to prevent the (G)MR element from ever being subjected to potentially damaging uncontrolled current transients. Test equipment used by any facility that deals with (G)MR heads must necessarily be evaluated for its potential to introduce undesirable current transients. The nature of the devices used to measure current transients can lead to misinterpretation of test equipment safety. It is important to understand both how to measure current transients and whether or not these events will damage an MR element. This paper defines and discusses the nature of a true current transient, explains the proper methods for measurement and interpretation of these events, and discusses how they may or may not relate to damage of an MR head.