The Static Stability of Half-Bubbles

Abstract

A variational model is used to calculate the static stability limits and equilibrium properties of “half-bubbles,” magnetic domains residing on one surface of a magnetic bubble material platelet. Stability is achieved through the presence of gradients in the domain wall energy density and/or saturation magnetic moment. The model evidences two distinct types of instability behavior separated by a critical value of the wall energy density gradient. Unlike the standard cylindrical domain, the half-bubble has a minimum stable value of the ratio of domain diameter to height. The half-bubble is shown to possess a number of properties which make it potentially useful for device applications. It is self-biased by its closure wall and in some cases is stable in zero external bias. Bias margins are of the same order as those for the standard cylindrical domain. It stabilizes on only one platelet surface, and its properties are independent of both material thickness and of minor irregularities on the second surface. In addition, its structure may be advantageous in avoiding the undesirable properties of hard bubbles.