Magnetoelastic dependence of switching field in TbFe-FeCo giant magnetostrictive spring-magnet multilayers

The role of magneto-elastic interactions in controlling the magnitude of switching field and coercivity is investigated using sputter-deposited TbFe/FeCo multilayers. In the absence of long-range anisotropy in amorphous TbFe layers, along with negligible magneto-crystalline anisotropy in FeCo layers, reversal behavior in these multilayers is largely determined by stress-induced anisotropy. Results show that magneto-elastic constraints at the TbFe-FeCo interfaces arising due to different values of saturation magnetostriction in adjacent layers lead to biaxial stresses. This manifests itself as highly square and similar M-H loops measured in different directions in the plane of the films. The measured values of coercivity in these films (between 4.5 and 7.0 mT) are found to be in close agreement with theoretical coercivity values predicted on the basis of biaxial stress-induced anisotropy. Biaxial stresses resulting in corresponding stress-induced anisotropy were found to have interesting consequences vis-a-vis magnetization reversal. In particular, self-organized domain patterns are formed during reversal which are mediated by local stress state in the films. (C) 2000 American Institute of Physics.