Magnetothermal instabilities in an organic superconductor

Abstract:

We have studied the occurrence of magnetothermal instabilities in a $\kappa - {(BEDT - TTF)_2}Cu[N{(CN)_2}]Br$ single crystal during field sweep magnetization experiments, equivalent to short time relaxation studies. We find instability behaviour in good agreement with a recent model by Mints, for a non-linear E(J) characteristic. In particular, we find that a decrease of the dynamic relaxation rate, characterizing the effective activation energy, precedes the unstable regime. We point out formal analogies between such instabilities and the general predictions for flux avalanches.