Temperature-dependent dynamics of stochastic domain-wall depinning in nanowires

The temperature dependence of domain-wall depinning in permalloy nanowires is investigated by measuring depinning fields and corresponding depinning times as a function of the external magnetic bias field. Domain walls are pinned at triangular notches in the nanowires and detected noninvasively by Hall micromagnetometry. This technique allows one to acquire depinning-field and depinning-time distributions in the temperature range between 5 and 50 K and thus to determine the stochastics of the depinning process. The results are discussed in terms of the Néel-Brown model for thermally activated magnetization reversal, assuming a single energy barrier to overcome. In general, the cases presented deviate from this description and give a clear indication that a more complex term for the energy landscape of domain-wall depinning at constrictions in nanowires is obligatory.