Magnetoresistive (MR) head achieves high areal density in a magnetic recording system due to high sensitivity of the magnetic field. The high sensitivity of MR sensor, however, potentially causes an instability of readback signals. This instability appears as a variation of the output wave form during alternating reading and writing processes. In this study, MR heads were measured by a new technique that used rotational applied field. This technique is intended for checking the stability of magnetic domains against the arbitrary direction of the magnetic field. As a result, deviations of transfer curves for the MR sensor correlated to variations of the output voltage. This deviation seems to be caused by the Barkhausen jump in MR sensors. In order to analyze the Barkhausen jump, a simulation using the Landau–Lifshitz–Gilbert (LLG) equation was carried out. A calculated transfer curve of the MR sensor was similar to a measured curve, and it included two different origins of the Barkhausen jump. The first type of jump happened in the MR film. A rotational applied field generated domain walls in the active region of the MR film. The second type of jump occurred in the soft adjacent layer (SAL) film. The appearance of vortex domain walls changed the bias field from the SAL film, and then it forced a bias state variation in the MR film. The first type and second type of Barkhausen jump showed 0.05 and 0.01 Ω resistance change, respectively. But, in reducing the MR sensor height, the Barkhausen jump was suppressed, even in the case of a small domain stabilizing bias field.
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