Optical Absorption Spectrum of ErCrO3

We present a study of the optical absorption spectrum of ErCrO3 as a function of temperature and magnetic field. Three types of processes are observed: (1) creation of a Cr+3 R-line exciton, (2) excitation of the Kramers-split Er+3 single-ion states, and (3) the simultaneous excitation of a Cr+3 exciton and a spin-flip of the Er+3 ground state. At 9°K there is a discontinuous change in the Cr+3 and Er+3 spectra due to a Cr+3 spin reorientation. The selection rules on the Davydov-split Cr+3 exciton states are shown to yield information about the magnetic symmetries. The magnetic dipolar contributions to the Er+3 Kramers splittings are calculated and shown to be insufficient to explain the large observed splittings, which implies an additional Er+3–Cr+3 interaction and a possible Er+3–Er+3 interaction.