Modified strong dipole-proton coupling model and local properties of EPR probe in KDP-type ferroelectrics

Abstract

The modified strong dipole-proton coupling (MSDPC) model, which predicts several static and dynamic dielectric properties of KDP-type ferroelectrics, is used to investigate the properties of the paramagnetic center SeO 4 3− introduced in the KH2PO4 (KDP) and KD2PO4 (DKDP) lattice as a local probe in an electron paramagnetic resonance experiment. Paramagnetic center is treated within the MSDPC model as a soft impurity, with anA probe value of the elastic constant for the dipolec-component induction lower than theA value for the original PO 4 3− group. ForA probe=0.45A, the molecular dynamics simulations in the paraelectric phase of KDP and DKDP show the effective local double-well potential of the probe, and the temperature dependence of the calculated correlation time τ for the dipole reorientational jumps over the barrier can be fitted by the Arrhenius law. The obtained Arrhenius parameters for KDP are close to the experimental ones, and the experimentally detected higher activation energy in DKDP is reproduced. Also, the high-temperature line broadening and the temperature dependence of the77Se hyperfine coupling observed in experiment are discussed within the MSDPC model.