Dresden 2009 – wissenschaftliches Programm

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DF: Fachverband Dielektrische Festkörper

DF 8: Glass I

DF 8.7: Vortrag

Dienstag, 24. März 2009, 12:00–12:20, WIL B321

Length scale effects in amorphous metals investigated by mechanical loss spectroscopy — •Dennis Bedorf, Moritz Schwabe, and Konrad Samwer — I. Physikalisches Institut, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany

Glassy behavior is, in a common assumption, affected by inhomogeneities in internal dynamics. Recent computer studies using molecular dynamics have revealed dynamical heterogeneities on an atomic length scale ( Teichler et al. , Zink, Mayr[1] and Neudecker). During a shear process shear transformation zones with a radius of about 1.5 nm and string like fluctuations with several nm length occur. Both processes are supposed to be surrounded by an Eshelby-Stress-Field to memorize configuration via the elastic energy [2].

Mechanical spectroscopy using double-paddle-oscillator technique enables us to study mechanical loss in thin films. For this study we choose glassy PdCuSi. The dependence of the loss on temperature and film thickness delivers the activation of certain processes in particular α- and β- process (wing). Our measurements show a disappearance of the β- process below 50 nm. We discuss this finding in terms of stress fields competing with spatial confinement and surface annihilation.

This work was supported financially by DFG, SFB 602 and Leibniz Programm.

[1] M. Zink, K. Samwer, W. L. Johnson and S. G. Mayr,

Phys. Rev. B 73, 172203, (2006).

[2] J. S. Harmon, M. D. Demetriou, W. L. Johnson and K. Samwer,

Phys. Rev. Lett. 99, 135502, (2007).