Length scale effects on relaxations in metallic glasses

The relaxation mechanism of amorphous thin films (PdCuSi) is studied by mechanical loss spectroscopy using the double-paddle-oscillator at 5.4 kHz. As in bulk material we can identify the primary (α) and secondary relaxation modes (β) for thick films (200 nm). By reducing the film thickness below 30 nm the loss of the secondary relaxation is vanishing. We discuss the results by the Eshelby-stress field surrounding the string-like excitation reaching the free surface which looks like a merging of the primary relaxation and the secondary relaxation due to size effects.