Extra-low-frequency noise in giant magnetoresistance recording heads

Extra-low-frequency (ELF) noise was studied in flyable, shielded giant magn etoresistance heads using a novel, ultralow-noise amplification system. The noise power spectral density had a 1/f character over wide frequency and s ense current ranges. The noise was mainly magnetic in origin. It, however, did not follow Hooge's formula. Random telegraph noise (RTN) was observed a fter moderate current stressing. The characteristic dwell times of the two- level RTN switching changed with applied field, sense current, and temperat ure. We consider the ELF noise as a sensitive diagnostic tool, since deviat ions from the 1/f dependence signal the existence of undesirable magnetic s tates. (C) 1999 American Institute of Physics. [S0021-8979(99)33008-5].