Impedance of a ferromagnetic sandwich strip

A theoretical approach for calculating the impedance of a three-layer sandw ich, consisting of two metallic ferromagnetic layers separated by a non-mag netic conductive layer, is presented. The Maxwell equations for the electro magnetic field coupled with the Landau-Lifshitz equations for the magnetiza tion dynamics are solved, which enables one to describe the system over a w ide frequency range, including the ferromagnetic resonance. Two sandwich st rip structures are analyzed, both having thickness much less than the width , and the width much less than the length: a "closed" structure with the ma gnetic film closing at the edges along the width, and an "open" structure w ithout flux closures where all the layers have the same width. The impedanc e for the two structures is calculated and analyzed as a function of the ph ysical parameters of the device and frequency. The "closed" structure is mo re efficient magnetically and exhibits a highly inductive response to much higher frequencies than the "open" structure. The analytical results obtain ed are directly applicable to practical design of GHz inductive components. (C) 2001 American Institute of Physics.