Effect of a magnetic field pulse on ultrafast magnetization reversal in a submicron elliptical Permalloy thin film

The characteristics of a magnetic field pulse, its magnitude, direction, and rise and fall time on the mechanism of ultrafast magnetization reversal have been studied by micromagnetic simulations. An elliptically shaped, Permalloy thin film, having dimensions of 400 nm long axis, 112 nm short axis, and 3.2 nm, thickness, was considered. A plot of the magnetic field pulse components describes three types of reversal behaviors, quasicoherent, incoherent, and nonreversal. The optimum magnetic field pulse for the suppression of magnetization ringing is found in the incoherent precession area by finding the lowest remanent total energy at the moment the pulse is cut off. The rise and fall time of the pulse has a significant effect on the reversal behavior only in the incoherent precession region. In this region, whether a reversal can occur depends on the rise time of the pulse. Extending the rise and fall time of the pulse, in the noncoherent rotation region, does not lead to a clear change of the remanent total energy but a rise time longer than 50 ps does result in a distinct increase in the remanent exchange energy, which enhances the magnetization ringing. (c) 2007 American Institute of Physics.