A study of voltage fluctuation, noise and magnetic instability in spin valve GMR recording heads

An abnormal voltage fluctuation in spin valve GMR recording heads is reported. Methodologies for detecting the fluctuation using a spin stand or an MR transfer curve tester are presented and used to study the phenomenon as a function of bias current and magnetic field. It is shown that the fluctuation only occurs within narrow ranges of sensor bias current, is suppressed by an external magnetic field and can result in a 7 dB increase in the noise floor at 10 MHz. Low field transfer curves show that the voltage fluctuation is the result of magnetic instability.