A GdFe/TbFe/GdFe trilayer constitutes a magnetic nanostructure: the domain wall junction. With this device, we studied the propagation of 180° domain walls from one GdFe layer to the other, through a single planar defect the thin TbFe layer that acts as an artificial energy barrier. Before crossing the energy barrier, by thermal activation, due to the applied magnetic field, the domain walls are compressed against the TbFe layer. Nucleation, compression, and propagation phenomena of 180° domain walls are presented. The behavior of domain walls is followed from the electrical resistivity of the sample. A parallel between the domain-wall decompression and the exchange biasing problem in ferromagnetic/antiferromagnetic bilayers is proposed.