Giant magnetostriction of TbFe monolayers with improved field-induced sensitivity

Giant Magnetostriction (GMS) reported until now in thin films using rare ea rth-transition metal RM2 (R = Tb, Sm, and hP = Fe, Co) compounds, presents in most of cases an isotropic or quasi-isotropic magnetoelastic (ME) behavi or, A large change of the ME coefficient b under the lowest possible extern al field is required in order to improve the sensitivity of these materials which are interesting for their application in the microelectromechanical systems (MEMS). The present paper shows the possibility of improving strong ly both the ME coefficient and sensitivity, Optimized ME properties are cor related with the sputtering parameters such as the RF power P-rf and the sp uttering gas pressure P-Ar.The magnetostriction increases with P-rf up to v ery large saturation values not observed until now in TbFe films (Deltal/l = 1300 ppm or b(gamma ,2) = 50 Mpa at 20 kOe) due to a structural change fr om amorphous at low P-rf to crystallized phase at a high P-rf as confirmed from XRD. When a bias magnetic field H-d is applied on the film during depo sition it is observed a strong change in the structural, elastic, magnetic and ME properties. N-d keeps the amorphous phase even at high P-rf which in duces a reduction of the ME "linewidth" but an increase of the GMS sensitiv ity.