Abstract: The influence of the magnetostatic interaction between vertical Bloch lines (VBLs) on the stability of hard domains in garnet bubble films subjected to a magnetostatic bias field is investigated. The collapse behaviour and the stripe-to-bubble transition behaviour of circular hard domains as well as the relationship between these two behaviour are studied experimentally. The domain wall energy formula of the circular hard doamins is improved by adding a magnetostatic interaction energy term between VBLs. Then, some experimental phemomena of hard domains subjected to a bias field, which have remained unclear for many years, are interpreted qulitatively. Based on these grounds, a method is proposed for estimating the number of VBLs in the walls of hard domains. Finally, the dependence of the hard domain kinds on temperature was interpreted qualitatively by using above improved theory.

Key words: magnetic bubble, magnetic domain wall, Bloch line