The thermodynamics of physical and magnetic changes to AMR sensors from EOS at variable pulse widths

Damage from Electrostatic Over-Stress (EOS) to shielded anisotropic magnetoresistive (AMR) sensors used for magnetic tape storage devices were studied using square wave voltage pulses. Changes to the sensor´s physical and magnetic properties were measured after each of a number of sequential pulses. The change in sensor resistance and magnetic amplitude and asymmetry were each fit to a thermodynamic model. Two processes were observed: Annealing and degradation, with respective activation energies of 2.1plusmn0.1 eV and 2.9plusmn0.1 eV. The annealing was associated with a slight decrease in sensor resistance and an increase in AMR asymmetry. The degradation was associated with a decrease in AMR asymmetry and amplitude, and an increase in sensor resistance.