Analysis of Current Distribution in Magnetic Film Inductors

We have extended our electromagnetic model for high-frequency magnetic film inductors to account for driving current redistribution in structures where the conductor and the magnetic film are in direct electrical contact. We consider a stripe conductor of rectangular cross-section enclosed in a magnetic film. A potential difference of fixed amplitude is applied to both the conductor and the magnetic film. Maxell's equations for this geometry are solved analytically, and a simple expression for the impedance is obtained. The inductance at low frequencies (Q1) is practically unchanged compared to the case where the magnetic film is insulated from the conductor. However, the maximum achievable quality factor is found to be higher than that for the insulation case, regardless of the fact that a larger portion of the driving current flows through the magnetic film. Ten-fold inductance enhancements are achievable for thin (~100 nm) magnetic films, with quality factors Q>10 at ~1 GHz. Magnetic film inductors without insulation layers are simple in fabrication and promise large technological advantages.