Inverse Magnetostrictive Effect in Ni<SUB>x</SUB>Fe<SUB>1-x</SUB> (1≤ x ≤0.8) Thin Films Deposited on a Polypropylene Substrate

Abstract

The magnetostriction effect is a unique phenomenon observed in magnetic materials due to applied stress. The permeability μ of the magnetic material increases or decreases depending on the sign of the magnetostriction coefficient λ based on the direction of the applied stress. For example, nickel has a negative λ, whereas iron has a positive λ for the same tensile (+) or compressive (-) stresses. However, the magnetostriction effect is reported to disturb the functionality of some spintronic applications, such as magnetic sensors and actuators, under the influence of an external magnetic field. Therefore, suppression of the magnetostriction effect is a challenge in developing flexible spintronic devices. In this study, the magnetostriction effect of the NiSUBx/SUBFeSUB1-x/SUB thin films was investigated under different stress conditions. The composition of the thin film was manipulated by varying the deposition thickness of nickel and NiSUB8/SUBFe₂ targets using a co-sputtering system. Magnetization reversal behaviors of the NiSUBx/SUBFeSUB1-x/SUB thin films were observed under the influence of an external magnetic field by using a vibrating sample magnetometer (VSM), before and after the application of bending stress. The negative magnetostriction effect of nickel was decreased by increasing the iron composition in the thin film, owing to the opposite sign of the magnetostriction coefficient. Finally, an extremely low magnetostriction was achieved at x = 0.8. The results of this study suggest that the magnetostriction effect can be controlled by varying the composition of the thin films and a sufficiently small magnetostriction effect can be observed at the permalloy composition between nickel and iron.