Spectroscopic Study of the Multiferroic LiCoPO4: Magnetostructural Phase Transition

Abstract

The low-frequency excitations of the LiCoPO₄ multiferroic have been studied. New lines of various origins have been observed in the transmission spectra below the temperature of antiferromagnetic ordering, which is accompanied by the appearance of spontaneous electric polarization. Most of these lines correspond to magnetic excitations. The appearance of new phonons in the antiferromagnetic state has been detected for the first time, which makes it possible to classify the phase transition as a magnetostructural phase transition. Information on the frequencies of infrared-active B_1u and B_2u modes of LiCoPO₄ has been obtained for the first time. These data are in good agreement with the ab initio calculations.