Current density and ac field effects on 1/f noise in spin valve sensors

Low frequency noise in patterned NiFe/Co/Cu/Co/FeMn (Delta R/R>9%) spin val ves was investigated. The spin valves were sputter deposited and patterned by lift-off to form 75 mu m x 1000 mm lines. Noise power spectra were measu red in the frequency range from 1 Hz to 10 kHz for ac and dc fields applied both parallel and perpendicular to the easy axis. An increase in the low f requency noise power spectrum was observed for an ac field applied along th e easy axis. Increasing the ac drive frequency from 500 Hz to 5 kHz reduced the low frequency noise power to near the zero field background level. (C) 1999 American Institute of Physics. [S0021-8979(99)48508-1].