Multiferroic and phonon properties near the phase transitions of pure and ion-doped Ca3Mn2O7

Abstract

ABSTRACT The magnetic, dielectric and phonon properties of CaMnO are investigated using a microscopic model and the Green's function technique. Electrically induced decrease of the magnetization M is observed which is an indirect evidence that CaMnO is a multiferroic material. The dielectric function has an anomaly at the Nel temperature and a broad peak at the Curie temperature . increases with increasing magnetic field. M and are enhanced by Li ion doping, whereas reduced by Ti ion doping due to different strain caused by the doped ions which changes the exchange interaction constants. increases with increasing Ti concentration. The temperature and magnetic field dependence of the phonon energy and damping for the A mode = 624 cm are studied. Both show a kink at due to the strong spin–phonon interaction. The kink disappears applying a magnetic field.