Inverse Magnetostrictive Effect in NixFe1-x (1≤ x ≤0.8) Thin Films Deposited on a Polypropylene Substrate

The magnetostriction effect is a unique phenomenon observed in magnetic materials due to applied stress. The permeability mu of the magnetic material increases or decreases depending on the sign of the magnetostriction coefficient lambda based on the direction of the applied stress. For example, nickel has a negative lambda, whereas iron has a positive lambda 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 NixFe1-x thin films was investigated under different stress conditions. The composition of the thin film was manipulated by varying the deposition thickness of nickel and Ni8Fe2 targets using a co-sputtering system. Magnetization reversal behaviors of the NixFe1-x 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.