  Characterizing the optical response of magneto-optic and magnetic materials
usually relies on semi-classical models (e.g. Lorentz oscillator model)
involving few parameters or models based on a detailed quantum mechanical
description of the underlying response. These models typically involve a few
parameters that are estimated via fitting the experimental data to provide a
qualitative understanding of the underlying physics. Such a few-parameters
fitting approach falls short of accurately capturing all elements of the
complex-valued permittivity tensor across a range of wavelengths. Accurate
characterization of the permittivity tensor elements across a broad range of
wavelengths is invariably imperative for designing optical elements such as
isolators, circulators, etc. Here, we propose and demonstrate a ubiquitous and
accessible method based on a combination of spectroscopic ellipsometry and
spectroscopic Magneto-Optic Kerr Effect (MOKE) measurements coupled with
rigorous numerical parameter extraction techniques. To this end, we use the
combined MOKE ellipsometry measurements conducted at different angles of
incidence with a gradient-descent minimization algorithm to provide the inverse
solution to the complete dielectric permittivity tensor. Further, we
demonstrate model re-verification to ensure the estimated dielectric
permittivity values reliably predict the measured experimental data. Our method
is a simplified bench-top counterpart to the otherwise complex measurement
systems.
