STUDIES OF CHROMIUM-DOPED SODIUM AMMONIUM-SULFATE DIHYDRATE .2. ELECTRON-PARAMAGNETIC-RESONANCE AND DIELECTRIC SUSCEPTIBILITY MEASUREMENTS OF CHROMIUM-RICH REGIONS

Some crystals of chromium-doped sodium ammonium sulphate dihydrate (SASD) appear to be divided into regions of darker and regions of lighter blue coloration. Crystal specimens cut from the darker regions have been investigated. Their EPR spectrum exhibits, in addition to the beta-site previously measured, a new site, labelled beta' because of its similarity to the beta-site. The spin-Hamiltonian parameters of the beta'-site have been measured at 300 K, and the temperature dependence of the spin-Hamiltonian parameter D has been measured from 300 K to 77 K. In contrast to the alpha-site described previously, the beta'-site shows a marked doubling below 92 K, corresponding to a change in D. The temperature dependence of the dielectric susceptibility shows a marked change at 204 K, only very slightly noticeable in undoped SASD, which correlates with a change of slope in the temperature dependence of D measured by EPR.