  The magnetoimpedance effect is a versatile tool to investigate ferromagnetic
materials, revealing aspects on the fundamental physics associated to
magnetization dynamics, broadband magnetic properties, important issues for
current and emerging technological applications for magnetic sensors, as well
as insights on ferromagnetic resonance effect at non-saturated magnetic states.
Here, we perform a theoretical and experimental investigation of the
magnetoimpedance effect for the thin film geometry in a wide frequency range.
We calculate the longitudinal magnetoimpedance for single layered, multilayered
or exchange biased systems from an approach that considers a magnetic
permeability model for planar geometry and the appropriate magnetic free energy
density for each structure. From numerical calculations and experimental
results found in literature, we analyze the magnetoimpedance behavior, and
discuss the main features and advantages of each structure. To test the
robustness of the approach, we directly compare theoretical results with
experimental magnetoimpedance measurements obtained in a wide range of
frequencies for an exchange biased multilayered film. Thus, we provide
experimental evidence to confirm the validity of the theoretical approach
employed to describe the magnetoimpedance in ferromagnetic films, revealed by
the good agreement between numerical calculations and experimental results.
