Studies of chromium-doped sodium ammonium sulphate dihydrate: I. Electron paramagnetic resonance of Cr3+

Abstract

Electron paramagnetic resonance (EPR) Of Cr³⁺ ions has been observed in single crystals of sodium ammonium sulphate dihydrate (SASD) doped with chromium. At 300 K the spectrum is relatively simple, exhibiting two main different sites, labelled alpha and beta . The spin-Hamiltonian parameters for these sites have been measured. The relative concentration of different paramagnetic sites shows marked sensitivity to unknown factors in the crystal growth. On lowering the temperature the spectrum becomes very complex, making detailed study of the various sites, and changes at any phase transition, impossible to elucidate. None of the spectra shows a marked change at the ferroelectric transition temperature, T_c=92 K.