Stress-Induced Linear Dichroism of the ¹E^a Band in the Antiferromagnetic KNiF₃

Abstract

The stress-induced linear dichroism (SLD) of the ¹E^a band in the antiferromagnetic KNiF₃ is studied under the ⟨001⟩ and ⟨111⟩ stress. The large SLD, which is non-linear to the stress, is explained as due to the reorientation of the collinear spins toward the direction of the stress. The analysis of the SLD leads to the assignments of the structures of the ¹E^a band. The band located at 634.5 nm consists of an overlap of a T_1u phonon-assisted electric dipole transition and a magnon sideband. The band at 619.5 nm arises from an exciton-magnon-phonon transition.