Microstrip transmission lines with ferromagnetic Co-Ta-Zr cores are investigated in this paper. Compared to nonmagnetic devices, an increase in both inductance (×11) and quality factor (× 6) is achieved in the transmission lines. The role of the magnetic material's electrical resistivity and the effect of the shape-induced anisotropy field (created by patterning the magnetic film into narrow stripes) are discussed. It is shown that the nonuniform distribution of the shape anisotropy inside the Co-Ta-Zr pattern can be used to advantage by proper placement of the signal line, thereby increasing the ferromagnetic resonance (FMR) frequency of the magnetic core. Inductance enhancement is achieved at frequencies up to ∼10 GHz. © 2008 IEEE.