engleski

Investigation of local properties in hydrogen bonded ferroelectrics by employing paramagnetic probes and modified strong dipole-proton coupling model

Investigation of local properties in hydrogen bonded ferroelectrics by employing paramagnetic probes and modified strong dipole-proton coupling model B. Rakvin and D. Merunka Ruđer Bošković Institute, PO BOX 1016, 10001 Zagreb, Croatia KH2PO4, or KDP, as a representative of hydrogen-bonded ferroelectrics, has attracted scientific interest for a long time because its phase transition shows several quantum effects and has unclear mechanism. The paramagnetic centers (AsO44-, SeO43- or CrO44-) have been usually employed as a probe to study slow lattice dynamics and low-frequency (107- 1010 Hz) polarization fluctuations of the KH2PO4, KDP-, type hydrogen bonded ferroelectrics in the vicinity of the paraelectric-ferroelectric phase transition temperature, Tc . Although a several attempts have been made to describe dynamics behavior of paramagnetic probes, detailed theoretical description is still rather scarce. The modified strong dipole- proton coupling model and Monte Carlo calculation are employed to describe paramagnetic defect in hydrogen bonded ferroelectric. In the strong dipole-proton coupling model [1] and its modified version [2], it was assumed that protons, which do not interact among themselves, has excitation energies higher than kBTc and ħ0, where ħ0 is characteristic lattice frequency. Therefore, protons in adiabatic ground state only produce ferroelectric interaction in the lattice, while the difference in ground-state energies between proton and deuteron causes the isotopic effect (proton – deuteron exchange). Some of experimental results of paramagnetic probes were explained by applying classical approximation for the lattice motion within the modified model [2]. [1] H. Sugimoto, S. Ikeda, Phys. Rev. Lett. 67 (1991) 1306. [2] D. Merunka, B. Rakvin, Phys. Rev. B 66 (2002) 174101.

hydrogen bonded ferroelectrics; EPR spectroscopy

nije evidentirano