Achieving high magneto-impedance effect: Controlling the evolution of textures in FeNi thin films by thermal annealing

Abstract The controlled growth and tailorable magnetic properties of FeNi thin films are of critical importance for controlling the magneto-impedance (MI) effect. In this study, a Ti layer was introduced to eliminate thickness-driven perpendicular anisotropy in thick FeNi films and thereby preserve their magnetic softness. Furthermore, the temperature-driven anisotropy determined the in- and out-of-plane magnetization behavior in FeNi/Ti-based multilayers, and so dominated the MI properties of these films. The oriented (1 1 1) texture of the out-of-plane crystal structure was enhanced with increasing annealing temperature. This supported the formation of perpendicular anisotropy in FeNi films, and reduced their magnetic softness. The in-plane texture changed from a dominant (1 1 1) orientation to a (2 2 0) orientation with increasing annealing temperature. This appear to be related to magnetic properties of FeNi thin films, because a minimum in coercivity occurred at the critical temperature of the texture transition. Thus, the largest MI effect was obtained in the FeNi-based multilayer at this critical temperature. Moreover, the interdiffusion at higher temperature between the Ti layer and the FeNi layer should be considered, because the coercivities and saturation magnetization of permalloy films increase and decrease sharply at 520 °C.