Structural relaxation induced by passing electric current in amorphous Cu50Ti50 at low temperatures

Abstract

The effects of passing current i on the structural relaxation in amorphous ${\mathrm{Cu}}_{50}$ ${\mathrm{Ti}}_{50}$ annealed at 423 K were investigated at and below 413 K. On the scale of the electric field ε corresponding with i, for ε above the threshold ${\epsilon }_T$ (0.5 V/cm at 413 K and 0.7 V/cm at 373 K), the electrical resistance R of the specimens showed a dramatic decrease against elapsed time t, but for ε below ${\epsilon }_T$, R remained unchanged. After completion of the decrease in R, the specimens became brittle. These results suggest that a strong increase in topological short-range order (TSRO) which can be expected to occur for thermal annealings above 600 K was induced even below 413 K under ε<εT. An effect of hydrogen possibly contained in the specimens was found to be negligible for the present results. It was further found that the TSRO process under ε could be explained by the Johnson-Mehl-Avrami model and the application of ε caused, surprisingly, a strong decrease in the effective activation energy, 0.8 eV/(V/cm), for the TSRO process. This effect of ε cannot be explained by the usual electromigration mechanism.