Resistance measurement of GMR heads as a magnetic performance indicator

The resistance of spin valve GMR heads as a function of current was studied , which was correlated with the magnetic performances of heads. The "assist " current gives larger DC resistance of MR elements than the "against" curr ent. The physical origin of this resistance difference is the spin-valve (S V) effect due to current direction. The resistance difference is defined as Delta MRR- = MRR- - MRR+ where MRR- and MMR+ are MR resistances measured w ith negative (assist) and positive (against) current directions, respective ly. This resistance difference has a good correlation with MR amplitude of SV. As an application, it is shown that the resistance difference well refl ects the MR amplitude of electrostatic discharge (ESD) stressed GMR heads. In this study, a simple and new method was suggested to evaluate MR amplitu des of SV by measuring the resistance difference of GMR heads with a digita l multimeter (DMM). The method reported here can be generally used to scree n ESD-damaged heads and to evaluate the magnetic performance during various stages of the GMR head manufacturing processes and failure analysis. This method does not require any external magnetic field. Therefore, this can al so be used for accelerated life test of GMR heads in an oven, where the ext ernal magnetic field can not be easily applied.