Dynamics of ultrafast magnetization reversal in submicron elliptical Permalloy thin film elements

The micromagnetic dynamics of ultrafast magnetization reversal in elliptical Permalloy (Ni80Fe20) thin film elements is described. It is shown that coherent rotation and magnetization ringing in submicron Py elements can be controlled by adjusting the axis ratio of the ellipse, the thickness, and the angle of the magnetic field pulse. For the elliptical Py element with 400-nm-long axis, 200-nm-short axis, and 4.7 nm thickness, the nonuniform distribution of magnetization results from a strong in-plane, nonuniform demagnetization field during magnetization precession. It is the main reason magnetization ringing appears, even though the average values of M-y and M-z are equal to zero at the moment the pulse is terminated. The simulation results indicate that uniformity in the distribution of the magnetization during reversal is improved by reducing the length of the short axis from 200 to 112 nm, and reducing the thickness of the thin film from 4.7 to 3.2 nm. The modification in the geometric configuration of the element is found to effectively suppress the magnetization ringing.