DC resistance instability in magnetoresistive recording heads

A resistance instability under DC bias condition in anisotropic magnetoresistive (AMR) recording heads has been observed. AC-coupled reader output voltage fluctuation across the biased sensor shows a square wave pulse profile with pulse width ranging from 1 to 500 /spl mu/s. An irregular pattern of pulse amplitude, width, and occurrence has been observed. Such instability has been found sensitive to the bias current, but not to external magnetic fields up to 200 Oe. Surface treatment has been found effective in eliminating this instability in AMR recording heads. Intermittent shorting due to metal smearing has been suggested as the mechanism that supports the above observations.