Statics and dynamics in giant magnetostrictive TbxFe1-x-Fe0.6Co0.4 multilayers for MEMS

In the present paper, giant magnetostrictive (GMS) thin films have been investigated for future microelectromechanical systems (MEMS) purposes. To this end, flexural and torsional motions have been studied in low-field anisotropic GMS single-domain state (SDS) exchange-coupled TbFe-FeCo multilayers (ECML). The magnetoelastic (ME) coefficient b^γ,2 depends strongly on the ECML structures, compositions, and sputtering deposition parameters. GMS multilayers with a high b^γ,2 (18 MPa for TbFe₂/Fe_0.6Co_0.4 compared to 11 MPa for TbFe₂/Fe) were obtained with or without an in-plane easy axis with a controlled direction, and without any annealing postprocess. Dynamical excitations of the actuators have been investigated under various conditions. An enhancement up to a factor 5 of the oscillations compared to the TbFe-Fe multilayers is observed with the possibility to tune the flexural/torsional dynamical behavior of these cantilevers. The corresponding very large dynamical ME susceptibility of these improved uniaxial ECML gives the possibility to control GMS MEMS with further reduction of the excitation field down to a few oersteds.