Temperature Stability of Vertical Bloch Line Chains in the Walls of the First Kind of Dumbbell Domains

The “softening” process of the first kind of dumbbell domains (IDs) with the increase of temperature was experimentally revealed as follows: IDs first convert to ordinary hard bubbles (OHBs) through a partial loss of the vertical Bloch lines (VBLs) in their walls and then these OHBs convert to soft (normal) bubbles (SBs) through a further loss of VBLs. As a result, the critical temperature for the break down of VBL chains of IDs is apparently higher than OHBs.