Behavior of vertical-Bloch-line chains of hard domains in garnet bubble films

As a main micromagnetic structure of domain walls in garnet bubble films, vertical-Bloch-line (VBL) chains play an important role in the characteristics of hard domains. In the 1970s, their study progressed rapidly during the period in which bubble devices were developed. When ultra-high-density Bloch line memory (BLM) was proposed in 1983, VBL chain behavior again attracted attention. This review will introduce the early achivements focusing primarily on the results of the last decade. A convenient method of forming VBL chains, a new classification scheme of hard domains and the unsolved “number effect” of VBLs will be discussed. Various behaviors of VBL chains under static compression, and in-plane magnetic fields will also be presented. Finally, the temperature stability of VBL chains will be reported.