HIGH-SENSITIVITY, GMR, 1-MICRON WIDE, END-ON, GANGED, READ HEAD SENSORS

Multiple, high sensitivity, GMR rad hed sensors were made and experimentally evaluated. The sensors were 1 micron wide and 10 microns long with flux gathering tips that expanded to 1.5, 2.0, and 3.0 microns. The sensors were found to have saturated outputs of 1.6 mV per micron of length for sense currents of 2.5 mA. The sensors had a very high sensitivity of 0.7 % change in resistance per Oe of signal field because of the low effective anisotropy of the sensor material. Test were performed in a uniform field at a frequency of 5 KHz on sensors without shields. Fields of +-4 Oe were sufficient to provide excitation over the full linear range. The experimental GMR material had a M-R coefficient of 6 % and a anisotropy field of 5 Oe along the long axis of the sensor. The non uniform ternary magnetic layers were 55 A(o) thick and the copper middle layers were 25 to 30 A(o) thick.