Paraelectric resonance of Li doped KC1 single crystals

Abstract

Lithium ion impurities in potassium chloride form paraelectric defects which are crystal imperfections having a permanent electric dipole moment that can exist in one of several equivalent but geometrically different positions. The exact form of the defect is not yet known although experimental and theoretical work indicates the defect can tunnel from one equilibrium position to another thus leading to transitions between the resultant states. The process of stimulating electric dipole transitions between the energy levels is known as paraelectric resonance. Paraelectric resonance is the electrical analog to paramagnetic resonance. A microwave spectrometer with related equipment capable of observing paraelectric resonance has been designed and built and is described herein. Paraelectric resonance was observed at 29.1 GHz and at 1.3° K in KC1:Li+ samples for eight different electric field orientations. Transitions were observed for the following values of electric field. [see PDF for chart] Data was also obtained on the transition line widths and power saturation. Observations were made on KCl samples which had been melt doped with lithium and on samples which had been doped by diffusion. The transitions observed are not in good agreement with the simple tunneling models which neglect internal strains. More than the predicted number of lines appear for certain orientations of the electric field and fewer than the predicted number of lines appear for other orientations.