Displacive Movement of the Radical in TGS near the Curie Point

ESR spectra of γ-irradiated TGS were observed in both ferroelectric and paraelectric phases. The hyperfine splitting tensors of the rotating β-protons and the α-proton in the radical NH 3 \(Ċ\)HCOO - , were determined. The hfs tensor of the β-protons was varied when the crystal passed through the Curie point. From the temperature dependence of the spectrum, the frequency factor, f 0 and the activation energy E of the rotating β protons were determined to be 5×10 11 sec -1 and 0.17 eV, respectively. Near and above the Curie point, the experimental curve of log τ versus 1/ T deviates from the relation 1/τ= f 0 exp (- E / k T ). This means that near and above the Curie point, glycines 2 and 3 are placed at the positions of point symmetry as if they make a displacive transition and the spectral lines are superimposed. It was also found that the ESR spectrum of the radical \(Ċ\)H 2 COO - disappeared abruptly at about 80°C, suggesting the decomposition of the radical.