DYNAMICAL MEASUREMENTS OF NUCLEATION AND PROPAGATION IN A DOMAIN-WALLJUNCTION AT LOW-TEMPERATURE

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