Magnetic Effects in the Optical Spectrum of MnF2

Sharp optical transitions between the 6A1g (ground state) and the 4T1g(4G) levels of MnF2 have been studied as a function of temperature (2°–40°K) and magnetic field (0–10 kOe) in both emission and absorption. Properties suggesting that two emission lines are spin-wave sidebands are discussed. Temperature-dependent shifts of the spectra are attributed to the antiferromagnetic nature of the crystal. A simple molecular field model is presented which describes the magnetic field behavior of the absorption spectra.