Elliptical distortion mechanism for ballistic overshoot of bubbles

Abstract

A theory for ballistic overshoot of gradient propagated magnetic bubbles is described. The overshoot arises from the relaxation of transient elliptical distortion and is predicted to be of order nμγ-1r -10(r10+r20) where n is the number of vertical Bloch lines on the flanks of the bubble, μ the linear mobility, γ the gyromagnetic ratio, r0 the static bubble radius, r 10 the change in average bubble radius at the end of the drive and r20 the elliptical distortion at the end of the drive. If one assumes all Bloch lines punch through to form vertical Bloch lines, the theory can account within 50 percent for the observed ballistic overshoot of many as-grown films as a function of gradient pulse time,strength and bias compensation. Furthermore new data on the detailed time dependence of bubble behavior during overshoot shows a rough correlation between displacement and elliptical distortion.