Magnetic relaxation in GdFe/TbFe/GdFe trilayers: Dynamic study of the propagation of a 180 degrees domain wall through an artificial energy barrier

An experimental study of the dynamics of the propagation of 180 degrees dom ain walls from a first GdFe layer to a second GdFe layer through a very thi n TbFe layer is presented. In this system, TbFe constitutes a very hard mag netic layer that acts as an energy barrier. It is shown from relaxation and from quasistatic measurements that the propagation of the domain walls can be analyzed as the crossing of an energy barrier from a metastable state t o a stable state. The relaxation data can be fitted with a unique relaxatio n time, which is quite unusual in magnetism. The system is modeled by an as sembly of parallel and similar domain-wall junctions. The evolution of the energy barrier parameters with the thickness of the TbFe layer are reported .