Domain Wall Motion in Magnetic Thin-Film Heads Driven by High-Frequency Current

A domain wall motion is analyzed by calculating the time derivative of a Kerr signal waveform in the thin-film head. The Kerr signal is measured in a small 18×15-µm area with a 1 MHz coil current. It is found that the 180° wall moves a few microns in the direction of the magnetic field. In the observed area, one end of the wall moves before the other end. In the range of absolute currents of more than the critical value, wall motion does not follow the current change. Though the average velocity of the motion is about 4 m/s for a half cycle, the actual velocity is about 10 m/s.