Magnetoelastic interaction in magnetostrictive spring-magnet multilayers

Local re-orientation of magnetization and stress which occurs during changes of global magnetization in magnetostrictive multilayers is quite complicated. However, if the local magnetic state is known and if the multilayer is deposited on a typical substrate, the local stresses can be calculated. A general method for stress calculations is given and is illustrated for spring-magnet-type multilayers whose layers exhibit no magnetocrystalline anisotropy or are amorphous. When the substrate is isotropic, the stored elastic energy is the same for all magnetic domains. Consideration of other energies such as magnetoelastic, potential magnetic energy, and domain wall energy indicates that the domain structure must depend on entropy. As the applied magnetic field is varied, a variation in the local magnetoelastic anisotropy occurs for each region in the material.