Dynamical measurements of nucleation and propagation in a domain wall junction at low temperature

GdFe (1000 Angstrom)/TbFe (e)/GdFe (500 Angstrom) sandwiches, where the thickness e of the TbFe film can be as small as 2 Angstrom, constitutes a Domain Wall Junction (DWJ). In this device, a 180 degrees domain wall, nucleated in the thicker GdFe layer, crosses an artificial energy barrier (the TbFe layer), by thermal activation (above 1 K). DWJs constitute a model system for the study of nucleation, pinning and depinning of a domain wall, in both thermal activation and quantum regimes. In the present case, quantum tunnelling of magnetisation is suggested below 0.7 K.