Exchange-spring systems: Coupling of hard and soft ferromagnets as measured by magnetization and Brillouin light scattering (invited)

An experimental and theoretical study is presented of the normal magnetic m odes in spiral ferromagnetic structures. The bilayer system studied consist s of Fe layers (25, 50, 100, and 200 Angstrom thick) that are exchange coup led to 200 Angstrom thick SmCo films that have approximate to 200 kOe aniso tropies. The Fe spiral-induced by an external magnetic field that is applie d opposite to the direction of the magnetized film-results in a structure s imilar to that encountered in a Bloch domain wall. The magnetization and th e field dependence of the magnons in various Fe films are explained by the theoretical model. (C) 1999 American Institute of Physics. [S0021-8979(99)4 7008-2].