PARAMAGNETIC-SUSCEPTIBILITY OF ADDITIVELY COLORED CDF2-IN PHOTOCHROMIC CRYSTALS

The paramagnetic susceptibility K-para Of CdF2:In crystals with metast able indium centers has been measured in darkness after photobleaching the crystals in visible light in the temperature interval 4-300 K. Fo r crystals cooled in darkness to liquid-helium temperature K-para is w holly determined by the accompanying impurity Mn2+ with magnetic momen t J=5/2. Illumination of the crystals leads to the appearance of an in duced signal delta K-para due to the formation of centers with J=1/2. The results of the experiments indicate the absence of paramagnetism i n the deep state of the indium center and its existence in the shallow (donor) state, i.e., they confirm the two-electron (negative-U) natur e of the deep indium level in CdF2. (C) 1997 American Institute of Phy sics.