Optical Spectra of Rare-Earth Orthoferrites

Abstract

The rare‐earth orthoferrites form a class of optical materials having intrinsically good transmission in the infrared between about 1.3 and about 8 μ. In thin sections they have enough transparency to be useful in the visible region. Optical absorption loss can be less than α=0.5 cm^‐−1 in the infrared, but Fe valence changes can reduce the transparency drastically. Doping experiments with Sn, Bi, Sb, Mg, and H⁺ are reported and their effect on optical transparency is given.