1/f noise in saturated GMR heads

Abstract

The extra-low-frequency noise of GMR heads was measured at large saturation fields (∼10 kOe). It was 1/f in nature. The head resistance increased exponentially with applied cumulative voltage pulses when the amplitude was larger than 1 V. However, the noise did not change even after the head resistance increased by 18%. This could be explained if the noise was generated mostly from the contiguous junction areas. A supra-linear dependence of noise voltage on sense current was observed. The supra-linearity increased after the sensor height was reduced by lapping. Hooge's formula was shown to apply at low currents. The excessive noise at high currents and at reduced sensor height was attributed to current crowding, in particular, current crowding caused by current heating.