The Static Stability of Half-Bubbles

The current interest in cylindrical magnetic domains and their device applications has stimulated the search for such domains in a wide variety of materials produced by a number of growth techniques. In 1933 1934 THE BELL SYSTEM TECHNICAL JOURNAL, NOVEMBER 1972 some samples, Bobeck1 has observed domains of reversed magnetization which apparently do not penetrate through the entire thickness of the sample (Fig. 1). These domains, referred to as "half-bubbles," have four features which make them potentially attractive for device applications. First, they contact only one surface of the platelet in which they reside so that their properties should not be as critically dependent on surface preparation as those of the usual cylindrical domains. Second, as shown in this paper, their properties are independent of platelet thickness. Third, this article also shows that their top closure wall produces a self-biasing effect which makes external biasing unnecessary in some cases. Finally, Bobeck et al.2 have observed in two-layer films that domains having a closure wall do not exhibit the undesirable properties of hard bubbles, and it is a reasonable presumption that this property also pertains to half-bubbles. Bobeck1 has suggested that half-bubbles may be stabilized by the presence of gradients normal to the material surface in one or more of the material characteristics (e.g., domain wall energy density