Magnetic changes in GMR heads caused by electrostatic discharge

The effects of current transients on the magnetic response of GMR sensors is studied. It is shown that GMR sensors with an FeMn exchange layer exhibit large magnetic changes after a single ESD current transient. The energy which results in magnetic failure is only 0.9 nJ, which is much less than the 6 nJ which causes physical melting damage to the GMR sensor. These serious magnetic changes are explained in terms of resetting of the FeMn exchange layer direction due to the elevated temperature and internal magnetic field during the current transient. It is concluded that ESD stress testing of GMR sensors has revealed a new and important magnetic failure mechanism in GMR sensors.