Paramagnetic Resonance of S -State Ions in Strontium Chloride

Paramagnetic resonance spectra have been observed of Mn²⁺, Gd³⁺, and Eu²⁺ in single crystals of strontium chloride grown from the melt. The Mn²⁺ shows a very small cubic-field splitting a<1×10^-4 cm^-1 and a hyperfine structure constant of A=81.2×10^-4 cm^-1, indicating some covalent bonding. The Gd³⁺ and Eu²⁺ have cubic symmetry with splitting parameters, for Gd³⁺: c=±(39.6±0.1)×10^-4 cm^-1, d=∓(0.2±0.1)×10^-4 cm^-1, g=1.9906±0.001; for Eu²⁺: c=(52±5)×10^-4 cm^-1, A¹⁵¹=(34.5±{}0.3)×{}10^-4 cm^-1, A¹⁵³=(15.5±{}0.3)×{}10^-4 cm^-1, g=1.995±0.001.The smaller cubic field splittings in SrCl₂ compared with CaF₂ seem to favor a mechanism responsible for the cubic-field splitting which is linear in the crystal potential terms.