A STUDY OF MIG HEAD READOUT WAVE-FORM ASYMMETRY, USING MAGNETIC FORCE AND KERR MICROSCOPY

The cause of the readback waveform distortion in polycrystalline ferrite MIG heads was investigated by using a magnetic force microscope (MFM) and also a polarized optical microscope capable of micro-ellipsometry for grain contrast and Kerr microscopy for domain contrast. It was revealed that for high asymmetry MIG heads, relatively large leakage of magnetic flux associated with complex multiple domains exists at remanence in the leading-side ferrite surface adjacent to the gap. The strengths of the magnetic flux and the magnetic domain states change irreproducibly when coil current is repeatedly applied. Such a remanent flux associated with the complex remanent state of magnetization distribution in the ferrite can cause an inhomogeneous flux coupling between the head and the recorded track resulting in readback waveform asymmetry.