Temperature dependence of domain-wall depinning fields in constricted Permalloy nanowires

We use ballistic Hall micromagnetometry to determine depinning fields of domain walls (DWs) in Permalloy nanowires in the temperature range between 5 and 50 K. The walls are pinned in constrictions defined by a triangularly shaped notch on one side of the wire. The high sensitivity of the Hall sensor to local stray fields allows the detection of individual DWs and a distinction of different wall types. A strong temperature dependence of the depinning fields is observed that can be described by a model with a single energy barrier. For temperatures above 20 K, additional types of DWs occur. (C) 2008 American Institute of Physics.