Infrared reflectivity of BaMnF4

The polarized reflectivity of BaMnF₄ single crystals was measured in the 20–600 cm^–1 range for temperatures from 10 to 300 K. The results were evaluated using Kramers-Kronig analysis to obtain the dielectric function. The number of active modes in the high temperature polar phase (T>T_i 250K) is in agreement with group-theoretical expectation. In the incommensurate phaseT<T_i the number of active modes increases more than two times. All the results are in reasonable agreement with previous Raman and far infrared data.