Low energy excitations in multiferroic Ca3CoMnO6 in the far infrared.*

Ferroelctricity was recently discovered in Ca3CoMnO6 (Y.J.Choi et al., PRL 100 (2008) 047601) which is a quasi 1 D spin up-up- down-down system. We report the results of infrared (5-250 cm- 1) transmission study of multiferroic Ca3CoMnO6 as a function of temperature T (3-300~K) and magnetic field H (0-8 T). Two peaks are observed at and below T$_N=17$ K. Narrow peak at 35 cm-1 is observed at low T and is identified as the ground state feature. This feature is suppressed with raising T or in magnetic field and the other broad feature at 25 cm-1 emerges. Neither peak is split or shifted by magnetic field. We will discuss the possible origin of these two excitations.