Small Domain Structures in Magnetization Reversal Process of Write Head in Hard Disk Drives Observed by Strain Imaging

Detection and imaging of magnetic-field-induced strains using scanning probe microscopy enable us to observe magnetic domain structures. Using strain imaging, domain structures in a magnetization reversal process of a thin film write head in a hard disk drive were investigated by scanning the air-bearing surface of the head. An external magnetic field was applied by the head coil. In the process, a characteristic small domain structure appeared in several portions in the bottom pole of the write head. The domain structure was hemispherical with a diameter of around 0.6 µm, consisting of two opposite magnetizations in the direction of the applied magnetic field. The domain structures appeared under a head coil current of less than 10 mA but vanished at larger currents. The portions where the domain structures were created should impede smooth magnetization reversal.