Abstract
Structural relaxation in a ferromagnetic glass is studied assuming that the structural defects are well described by two-level systems (TLS). Two coupling mechanisms between defects and magnetic moments are considered. One is based on the non-collinearity of the spins on the amorphous ferromagnetic ground state and the other is the conventional magnetoelastic coupling. From the point of view of the defects, the magnon-TLS interaction gives origin to an additional relaxation mechanism and an indirect coupling between TLS. The resonant interaction between thermal magnons and defects renormalises their spin wave stiffness and for strong coupling structural relaxation causes an instability of the ferromagnetic phase.