An EMI Immunity Study of TMR Heads in Quasi-Static Tester due to the Direction of Sweeping Frequency
This report aims to investigate a comparative effect of Electromagnetic Interference (EMI) on recording heads due to sweeping directions of low-to-high and high-to-low frequencies. Four selected Quasi-Static Tester (QST) parameters; MR resistance, MR amplitude asymmetry, Barkhausen noise and Hysteresis, are used for monitoring the effect of EMI on Head Gimbal Assembly (HGA). It is undoubtedly found that the Asymmetry and Hysteresis parameters provide insufficient indication of EMI effect for both sweeping frequency directions. On the other hand, it is discovered that the sweeping direction of the low-to-high frequency is more effective to two test parameters; MR resistance and Barkhausen noise, than the other direction. The dramatic energy accumulation is possibly explained this phenomenon but this energy level is not high enough to cause the Hysteresis change.
A. Siritaratiwat et al., "An EMI Immunity Study of TMR Heads in Quasi-Static Tester due to the Direction of Sweeping Frequency", Solid State Phenomena, Vols. 152-153, pp. 447-450, 2009