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 (SA SD) appear to be divided into regions of darker and regions of lighter blue coloration. Crystal specimens cut from the darker regions have b een investigated. Their EPR spectrum exhibits, in addition to the beta -site previously measured, a new site, labelled beta' because of its s imilarity to the beta-site. The spin-Hamiltonian parameters of the bet a'-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 s hows a marked doubling below 92 K, corresponding to a change in D. The temperature dependence of the dielectric susceptibility shows a marke d change at 204 K, only very slightly noticeable in undoped SASD, whic h correlates with a change of slope in the temperature dependence of D measured by EPR.