Magnetostrictive Performance in Py/TbFe Coupled Bilayers: Dependence on Hard Layer Thickness

Magnetostrictive TbFe was chosen as hard layer, and the spin dynamics in the coupled bilayers Py(10 nm)/TbFe(t nm) (Py-permalloy; t=4, 7, 10, 30) were investigated by taking advantage of the engineering magnetostrictive strain under the constraints of the measurement. The dependence of the engineering magnetostrictive strain on TbFe layer thickness reflects a competitive process between the interfacial exchange interaction and the TbFe anisotropy. For the dominant interfacial exchange interaction in the coupled bilayers with 4 and 7 nm TbFe layer, coherent magnetization rotation of Py and TbFe layers is very similar to the behavior described by the Stoner-Wolfarth model. Magnetic hysteresis in the coupled bilayers with 10 nm TbFe layer and the decrease in the maximum engineering magnetostrictive strain in the coupled bilayers with 30 nm TbFe layer were observed.