  We present a simple semiclassical model to sustain that in europium
chalcogenides (EuX), Faraday rotation (FR) in the transparency gap is
proportional to the magnetization of the sample, irrespective of the material's
magnetic phase, temperature, or applied magnetic field. The model is validated
by FR and magnetization measurements in EuSe in the temperature interval
1.7-300K, covering all EuSe magnetic phases (paramagnetic, antiferromagnetic
type I or type II, ferrimagnetic and ferromagnetic). Furthermore, by combining
the semiclassical model with the explicit electronic energy structure of EuX,
the proportionality coefficient between magnetization and FR is shown to be
dependent only on the wavelength and the band gap. Due to its simplicity, the
model has didactic value, moreover, it provides a working tool for converting
FR into magnetization in EuX. Possible extension of the model to other
intrinsic magnetic semiconductors is discussed.
