Luminescence of magnetic excitons in orthorhombic MnF2 films

Photoluminescence has been measured from 100 to 300 nm epitaxial thin films of MnF2 prepared on Si(1 1 1) substrates and having α-PbO2 orthorhombic structural type. The dominant luminescence consists of a broad band peaking around 575 nm with a gradual tail extending to longer wavelengths. Weak spectral line features are observed on the short-wavelength side of the main band and are associated with magnon sidebands of Mn2+ excitons that are perturbed by Mg and Ca impurities. Of note is a blue shift (∼12 nm) of these sidebands when compared to their positions in bulk MnF2. The shift can be associated with different crystal field for Mn2+ ions in orthorhombic phase.