Radial expansion dynamics of a magnetic bubble domain

Abstract

High-speed laser photography was used in two measurements on the radial expansion dynamics of unichiral, S = 1 magnetic bubbles during and after the application of large 20-, 40-, and 57-Oe expansion pulses. The bubble diameter was photographed at varying intervals after the beginning of a 120-ns pulse and the chirality change resulting from the application of pulses of widths from 17.5 to 120 ns measured. Plots of the probability of chirality change versus pulse width were used to infer the rate of rotation of the magnetization within the wall. Results are compared with the one space dimensional Schryer-Walker model. The features of high-speed initial motion followed by a slower uniform average velocity agree between the model and the data, but the large transients predicted when the pulse leaves the bubble in the unstable Néel wall state were never observed. It is necessary to increase the Gilbert damping parameter a by fourfold in order to get quantitative agreement between the model and the diameter data. The rotation rate of the model and the data agree for the 57-Oe pulse but a fourfold a increase is required at the lower amplitudes.