Influence of the Heat Treatment Duration on the Critical Temperature for the Break-Down of Vertical Bloch Line Chains

For longer heat treatment duration(10 and 30 min), near and within the transition region, the softening fraction ρ has an obvious, but not very large increase and the increment for 30 min is greater than that for 10 min. As a result, the critical temperature T₀ is only lowered by 2～3°C for a typical sample. The above results indicate the existence of a quasi-static athermal instability, and the thermal activation of Bloch points is only of secondary importance.