EPR Spectra of Gd3+-Doped NdCl3·6H2O and PrCl3·7H2O

The paramagnetic resonance spectra of Gd³⁺‐doped NdCl₃·6 H₂O and PrCl₃·7 H₂O single crystals are studied at room temperature. A six‐line spectrum for H ‖ Z and a seven‐line spectrum for H ‖ X corresponding to ΔM=±1 transitions, are observed in the case of Gd³⁺‐doped NdCl₃·6 H₂O, whereas Gd³⁺‐doped PrCl₃·7 H₂O shows a seven‐line spectrum for H ‖ Z as well as for H ‖ X. The absence of the seventh line in the case of Gd³⁺‐doped NdCl₃·6 H₂O for H ‖ Z spectrum is explained as due to large zero‐field splitting between $\pm \frac{5}{2}$ and $\pm \frac{7}{2}$ levels. The angular variation of the observed spectra in ZX plane from θ=0° to θ=90° is studied and the spin‐Hamiltonian analysis is presented. A number of lines have been observed in the low‐field region in the case of Gd³⁺‐doped PrCl₃·7 H₂O and they have been analyzed as due to transitions with ΔM>1.