Electron Paramagnetic Resonance Spectra of Zinc-Doped Copper Acetate Monohydrate

The electron paramagnetic resonance of the copper—zinc pairs in zinc‐doped copper acetate monohydrate has been observed at 77°K by using an X‐band EPR spectrometer. Single crystals containing less than 1% zinc ions were grown from a slightly acidic aqueous solution containing about 75% copper acetate and 25% zinc acetate. The experimental results could be fit to the spin Hamiltonian: $$\mathcal{H}{\mathrm{=g}}_z{\mathrm{\beta H}}_z{S}_z{\mathrm{+g}}_x{\mathrm{\beta H}}_x{S}_x{\mathrm{+g}}_y{\mathrm{\beta H}}_y{S}_y{\mathrm{+A}}_z{S}_z{I}_z{\mathrm{+A}}_x{S}_x{I}_x{\mathrm{+A}}_y{S}_y{I}_y.$$ The values A_z=0.0147±0.006 cm⁻¹, A_x<0.0018 cm⁻¹, and A_y<0.0023 cm⁻¹ were measured for the doublet‐state cupric ions. The g values were found to be: g_z=2.344±0.005, g_x=2.052±0.007, and g_y=2.082±0.007. These results are consistent with the model proposed by Slichter, in which he has shown that the components of the hyperfine tensor should be twice as large for a doublet species as compared to the corresponding triplet species when the exchange integral J is much larger than the components of the hyperfine tensor. Since the microsymmetry at the cupric ion site is no higher than C_2v, the EPR results were interpreted by using the theory of Bleaney, Bowers, and Pryce for lower than axial symmetry. The optical data have been interpreted on the basis of weakly interacting cupric ions. A consistent explanation for the magnetic resonance data and optical data is discussed.