Proton Magnetic Resonance in CaCu(CH3COO)4·6H2O and CaCu(CD3COO)4·6H2O at Low Temperatures

The atomic positions of protons in water molecules and in methyl radicals have been determined by the angular variation of the proton magnetic resonance spectra at 38 MHz and at 4.2 K. The shift can be fitted by the dipolar interaction between the protons and electron spins which have the spin density of (80±5)% on the copper and (\(20{∓}5\))% on the four coordinated oxygens. About 0.03% of the spin density is deduced to be on the protons in the methyl radicals from the isotropic shift. In a temperature range down to 1.3 K, the shift with H o along the c -axis shows the crystal behaves as a pure paramagnet with a negligible Weiss constant. The possibility of one-dimensional exchange interaction is discussed.