Bordoni peaks in face-centered cubic metals at low temperatures

Two internal friction peaks discovered in pure aluminum at increasingly low temperatures, respectively by Lax and Filson and by Kosugi and Kino, are interpreted as different occurrences of the well-known Bordoni peak. The Lax–Filson peak is attributed to impurity assisted nucleation of thermal kink pairs; the Kosugi–Kino peak marks the onset of a new nucleation mechanism: the geometrical kinks (antikinks) rearrange themselves into superkink–antikink pairs in order to overcome the Schottky barriers. The experimental conditions for the direct observation of such peaks are discussed in some detail.