MAGNETIC-PROPERTIES AND ENERGY-TRANSFER IN THE LUMINOPHORS CAS-EU,CL

Studies have been performed on the magnetic properties and electron pa ramagnetic resonance (EPR) spectra of the small-crystal luminophors Ca S:Eu,CI. By comparing the EPR and magnetic susceptibility data we have determined that Eu enters into the CaS matrix primarily in the trival ent state Eu3+. We have found that the magnetic susceptibility of the sample with the lowest europium content (5 x 10(-3) at. %) has a sharp peak at T approximate to 5 K. A model is proposed of clusters into wh ich the europium ions in these luminophors can associate. On the basis of this model an explanation is given for the anomalous temperature d ependence of the magnetic susceptibility as well as a long list of oth er experimental facts (including peculiarities of the thermal luminesc ence). (C) 1998 American Institute of Physics. [S1063-7761(98)01005-1] .