Magnetic properties and microstructure of giant magnetostrictive TbFe/FeCo multilayers

Magnetostrictive multilayer films which combine exchange coupled giant magnetostrictive materials (amorphous $Tb0.4Fe0.6$⁠) and soft magnetic materials with large polarizations and considerable magnetostriction (crystalline $Fe0.5Co0.5$⁠) were prepared by magnetron sputtering. The microstructure and the magnetic properties of these multilayers were investigated as a function of the annealing temperatures and the corresponding film stresses. Giant magnetoelastic coupling coefficients (or magnetostrictions) are achieved at low fields, due to the magnetic polarization enhancement in such multilayers, the optimized stress state, and a suitable microstructure. For these optimized $Tb0.4Fe0.6(7 nm)/Fe0.5Co0.5(9 nm)$ multilayers a saturation magnetoelastic coupling coefficient of 27.5 MPa at 20 mT and a coercive field of 2 mT has been achieved.