Break Down of Vertical-Bloch-Line Chains in the First Kind of Dumbbell Domain Walls Subjected to an in-Plane Field

Experiments were statistically carried out on the behavior of the vertical-Bloch-line(VBL)chains of the first kind of dumbbell domains(IDs)in garnet bubble films subjected to an in-plane field,Hip.It was found that for IDs the critical in-plane field,(Hip)ID,above which their VBL chains disappear,is the same as that of ordinary hard bubbles(OHBs),H'ip.However,for IDS,the critical range of Hip for VBL chain softening is larger than that of OHBs.Besides,we also found some details of the softening process,e.g.,the collapse field range of the remaining IDs shrinks rapidly towards H_(0,mas),and this very narrow range can maintain until all IDs are softened.