Spin and lattice dynamics of multiferroic SrMn7O12 studied by THz and infrared spectroscopies at low temperatures and in magnetic field

Multiferroic SrMn 7 O 12 crystals are isostructural with CaMn 7 O 12 which is known for its unusual symmetry properties and a record-high spin-induced polarization. We studied SrMn 7 O 12 ceramics by THz time-domain and Fourier-transform infrared spectroscopies upon varying temperature and magnetic field. In the magnetic phases, we observed spin waves gaining strength from polar phonons; thus, they are assigned to electromagnons. We discuss the observed persistence of several low-temperature vibrational modes above the high-temperature phase transition, and the impact of atomic substitution with regard to CaMn 7 O 12 .