DOI: 10.1103/PhysRevB.89.045121

We report on the optical response of different magnetic oxides (manganites, ruthenates, and magnetite) and show that for photons with energies ≈1.5−3.5 eV the intensity of light reflected by these epitaxial oxide thin films is strongly modulated by magnetic fields. We argue that this behavior is related to the magnetopolaron physics, and the magnitude of the magnetoreflectance is a fingerprint and a measure of the electron-lattice coupling strength. Our research provides the basis for a fresh experimental approach to the physics of strongly correlated electronic systems.