Bias field dependence of domain drag propagation velocities in GdCoAu bubble films

Abstract

The bias field dependence of the velocity of bubble propagation by the domain drag effect was studied in a GdCoAu amorphous film. Bubbles in close-packed arrays were propagated by pulsing currents directly through a stripline of the material fabricated by photolithography and ion-beam milling. As bias field is increased, at given current and pulse width, the velocity decreases, passes through a minimum, then increases again. The domain drag drive field at a given bias is derived both from the critical current at which motion begins and from the slope of velocity with current. A theory for the domain drag drive field Hd of a bubble raft with infinite length along the current direction is derived, giving the simple result Hd /βjD = 1/2(d0/D) -(π/4√3)(d0/D)3, where β is the Hall angle, j is the current density, d0 is the bubble diameter, and D is the nearest-neighbor spacing. Experimental results from critical current agree approximately with the theory, but results from velocity slope with current are a factor of 3 too high.