Dynamics of amorphous film bubble devices

Abstract

A 10 ns pulsewidth stroboscopic laser system was used to study propagation and expansion of magnetic bubble domains in 2μ stripwidth GdCoMo amorphous film devices operating at frequencies up to 1 MHz. Expansion of domains under chevron expander structures, bubble translation in a pulsed gradient field, and bubble propagation in H-I bar loops consistently indicate that the mobility is about 2m/s-Oe under usual low-drive conditions. With high drives, the mobility is found to peak at about 20 m/s-Oe, and velocities as high as 500 m/s are measured. The mechanisms of this high mobility, high velocity wall motion are not understood, but the high velocities are observed during domain expansion under chevrons, during bubble translation in a pulsed gradient field, and during bubble propagation around large disks of permalloy. No evidence of hard bubbles or bubbles which deflect in a gradient field is found in these GdCoMo films. Error-free propagation of bubble data patterns around closed H-I bar loops for more than 109cycles at 1 MHz indicates that low error rates can be obtained in the amorphous films. Furthermore the propagation of bubbles around permalloy disks at average velocities of 180 m/s indicates that yet higher data rates could be achieved if sufficiently high frequency high power drivers could be developed.