Ultra-Fast Transmission Line pulse testing of tunneling and giant magnetoresistive recording heads

For the first time, damage thresholds for TMR and GMR read sensors were measured using pulses with widths ranging from 40 ps to 2.3 ns. The ultra-fast pulses were generated using a novel Ultra-Fast Transmission Line Pulsing (UFTLP) system. The damage voltage level for the TMR and GMR heads was about 0.6 V using 2.3 ns-wide pulses, and increased to about 2.0 V using 40 ps-wide pulses. However, the damage current level for the TMR design was about 4 mA, about an order of magnitude lower than the GMR design. It is important to measure the failure level using pulses with pulse widths less than 1 ns wide because write-to-read crosstalk can produce such transients during writing. It is concluded that damage to the reader from 500 ps-wide write-to-read crosstalk transients will occur if it exceeds approximately 1 V.