Domain wall velocity in YFeO<inf>3</inf>exceeding the walker critical velocity

Domain wall velocity in YFeO3single crystal platelets is measured by the bubble collapse method. The applied pulse width ranges from 100 ns to 7.8 ns, and the maximum applied field is 170 Oe. The wall velocity increases nearly monotonically with field up to 9000 m/sec, which exceeds the Walker critical velocity of 3600 m/sec estimated by Hagedorn. A weak knee is observed in velocity-field curves at about 4400 m/sec, which appears to be the indication of the Walker peak or critical velocity. The velocity break down theories due to coherent or incoherent precession of magnetization around the drive field analyzed by Slonczewski in high field are not applicable to this material. A possible mechanism in high field appears to be that the wall moves followed by a wake as proposed by Hagedorn and Gyorgy, and recently by Schlömann.