Irreversible Photoinduced Changes in Optical Absorption of YIG(Si4+) and YIG(Ca2+)

Abstract

Irradiation by white light at low temperatures produces drastic changes in the near‐infrared absorption coefficient of YIG doped with divalent Ca or quadrivalent Si. For Ca²⁺ doping, α increases; for Si⁴⁺ doping, α decreases on irradiation. In both cases the magnitude of the effect varies sharply with concentration. For YIG(Si) the results are interpreted in terms of the different properties of Fe²⁺ in sites that are near or far from the Si⁴⁺ ions. A similar model holds for YIG(Ca) with Fe⁴⁺ rather than Fe²⁺ being the important impurity. In both cases irradiation enhances occupation of the far sites.