Cubic and trigonal Cr+ defects in SrCl2:Cr

The authors present the results of a spectroscopic study of X-irradiated SrCl2:Cr. In crystals irradiated at 77K a cubic EPR signal is associated with Cr+ ions in a substitutional cation site. The spin-Hamiltonian parameters are g=2.0005+or-0.0003 and A=6+or-1 MHz for the 53Cr isotope. On heating the samples at temperatures above 200K the centres are destroyed, and at the same time a trigonal EPR signal is produced. This signal is due to Cr+ ions trigonally perturbed. The spin-Hamiltonian parameters are g=2.0005+or-0.0003, D=96.2+or-0.7 MHz and an effective hyperfine constant for the external magnetic field along the (100) direction of A(100)=61+or-1 MHz for the 53Cr isotope. These defects are also produced by irradiation at temperatures above 200K. Evidence for motional effects in this centre is also given.