Optical absorption of erbium in paramagnetic and antiferromagnetic states

The optical constants of polycrystal erbium in 56-293 K temperature range in 0.06 - 4.4 eV spectrum range are measured. The wide maximum in the frequency dependency of the light conductivity at 1-3 eV is accounted for by quantum interzone transitions. The samples cooling lower than the Neel point leads to slowing-down of the relaxation frequency temperature decay of optically active electrons anfd to the formation of a new absorption peak at 0.28 eV connected with s-f-exchange interaction