Déplacements d'une paroi de Bloch à 180° dans un monocristal de fer-silicium

Memory dependence of Barkhausen emission

“…The Kaiser effect is significant because it shows that in a wide variety of systems the onset of permanent hysteresis can be influenced by training procedures. Vergne and Cotillard (1977); Vergne, Cotillard and Porteseil (1981)). The essential components include the following:…”

“…Similar effects also occur in structural shakedown (Guralnick, Singh, and Erber 1984). Irreversible transitions such as Barkhausen jumps or acoustic emission pulses are always associated with the appearance of hysteresis (Schmidt and Pasztor 1977). The Kaiser effect is significant because it shows that in a wide variety of systems the onset of permanent hysteresis can be influenced by training procedures.…”

Irreversible processes in Bloch wall motion

“…1) and experimental setup have been described in detail in ref. Previous experimental results [2] suggest that 8 ~6/x, where 6 o is the thickness of the wall (2000 A) and x its velocity. The lattice defects in the s~~ple are mainly dislocations and subgrains ; they have been studied in a simllar sample by Schlenker et al [31 .…”

“…This work is a more detailed investigation of irreversible processes as a function of velocity. 2 . 1) and experimental setup have been described in detail in ref.…”

“…It can be concluded that, at low velocities, the wall moves as a flexible body by localized, statistically independent jumps. Dissipation at a higher rate becomes possible beyond the instability : this is illustrated by the fact that the Rayleigh coefficient b, which measures the dissipation in weak fields, is larger ~y one order of magnitude in the regime of large jumps [2] . For a jump to be thermally triggered, its activation time constant T has to be shorter than a characteristic duration of the experiment 8.…”