I. Introduction
Magnetoimpedance (MI) effect is the change of impedance in soft magnetic materials when we vary the magnitude of applied magnetic fields [1]–[3]. The origin of the phenomenon in the radio frequency (RF) range is the change of skin depth of the current applied to the specimen and is known to have a relation where is the frequency of the RF current and is the permeability of the material. MI effect has been mostly studied for possible applications to field sensing devices [4]. One of the most widely investigated types of soft magnets are those coated with Ni-Fe Permalloy thin films [5]–[7]. The most favorable property of Permalloy thin films for large MI effect is low coercivity [8]. Previous studies have shown that the grain size (L) of the thin film has a significant effect on ; specifically, for and for [9]. In an attempt to increase the change of MI in soft magnetic materials, we investigated the effect of organic additives on electroplated Ni-Fe Permalloy thin films and showed that their crystalline orientation, surface roughness, and could be adjusted by the species and concentration of the additives [10]. In particular, the reduction of Ni-Fe(200) in proportion to the concentration of the additives exhibited strong correlation with the decrease of and increase of MI [11]. Since MI effect arises from the motion of magnetization, magnetic anisotropy plays an important role in the magnitude of MI. Considering the shape anisotropy and miniaturization for possible application to a device, we fabricated thin wires of Ni-Fe Permalloy with varying aspect ratio and investigated the change of MI in the RF frequency range.