Dynamics of 1μm bubbles in ion-implanted contiguous disk structures

Abstract

The dynamic behaviour of 1μm bubble domains in double-layer garnet films in which the driving mechanism is by charged walls at ion-implanted pattern edges has been investigated using a 7 nsec pulsewidth stroboscopic laser system. Bubble propagation around circular and square-shaped structures, and between adjacent cusps forming part of a propagation loop was studied at frequencies up to 500 kHz. The data show that the tri-directional magnetocrystalline anisotropy of the driving layer has a strong influence on the dynamic behavior of the bubbles and is necessary to explain observed dependences of bubble velocity on propagation direction. The effective mobility μeff, of the charged wall coupled to a bubble was measured and found to be linearly related to the ion-implanted layer thickness t2, in agreement with theory. For a typical garnet composite of EuTmYGaIG/GdTmYGaIG with t2=0.4 μm, μeff∼280 cm/sec·Oe in comparison with a bubble domain wall mobility of ∼730 cm/sec·Oe. Expansion of domains along straight non-implanted edges, bubble translation and bubble propagation around disks consistently yield saturation velocities of 2000-3000 cm/sec in these composites.