Magnetic Layer / Nonmagnetic Layer / Magnetic Layer Sandwich Model Of Giant Magneto-impedance Effect In Theoretical Research

The large magnitudes of giant magneto impedance (GMI), together with a very high sensitivity at low fields, have prompted potential applications in information storage and micro-magnetic sensors. However, there are still lots of questions which remain to be answered in the theory research. A comprehensive theoretical description of GMI is very useful for better understanding of present experimental results and guiding further investigation.In this paper, a rigorous theoretical calculation of giant magneto-impedance (GMI) in the structure of sandwiched film is presented. The model of a single domain under in-plane uniaxial anisotropy is introduced to describe the GMI effect of sandwiched film. The theory is based on solving Maxwell's equations and the linear Landau-Lifhitz-Gilbert equation simultaneously. Considering the contribution of alternating anisotropy, we attempt to use three methods to deduce the expression for impedance. The three methods are as follows: using magnetic permeability under coordinate's transition to get the components of magnetic field in the quasi-static approximation; rotating the components of magnetic field with original effective permeability; solving magnetization vector of the Maxwell equation. Finally, we conduct the numerical calculation with variable parameters and compared the results with the three methods.The main results are as follows: we get the same regulars with three methods which are agreed with experimental results. In these three methods, the components of the permeability tensor and the approximate conditions are both different, so it gives the different curves even under the same conditions. Therefore, each method is limited to specifically materials and range of parameters. The results calculated offer reference for designing sandwich films in experiment.