Paraelectric Resonance of OH−Dipoles in KCl

Abstract

The theories of magnetic and electric susceptibilities have many features in common and, in fact, in Van Vleck's 1 classic exposition of the subject, both are treated on an equal footing. With the advent of adiabatic demagnetization, paramagnetic resonances, masers, and other devices, paramagnetism completely overshadowed its electric counterpart. More recently systems comprising electric dipoles embedded in ionic crystals have attracted renewed attention. 2 " 10 Cooling by adiabatic depolarization of electric dipoles has been demonstrated, 2 ' 5 ' 8 and the energies of the dipoles in an external electric field have been determined indirectly from their optical 3 and thermal properties. 8 ' 10 In the present note we wish to report on the resonance absorption (paraelectric resonance) of OH"" dipoles in KC1 in an externally applied dc and microwave electric field.The possibility of observing the paraelectricresonance transitions was first mentioned by Kuhn and Llity. 5 Brief reports on their observation have been given by Dreyfus and Bron 11 and Shepherd and Feher. 12 ? 13 These observations were made at a microwave frequency of ~9 kMc/sec. At this frequency the lines can at best be only partially resolved and not all the transitions can be covered. The present experiments were performed at a frequency of 35 kMc/sec. The improved resolution enabled us to determine the value of the zerofield splitting and the dipole moment (uncorrected for local field effects) and to estimate the dipole-lattice relaxation time at one temperature.The OH"" ion is introduced as an impurity into the KC1 lattice and substitutes for the Cl~ ion. 14 The dipole moments of the OH"" ions orient themselves along the six (100) directions. 3 The application of an external electric field changes the energies of the different dipolar orientations. Resonant transitions between different energy levels can then be induced by a microwave electric field. In order to observe these transitions, the samples 15 were placed into the E field of the microwave cavity or wave guide of a conventional electronspin-resonance spectrometer. The applied dc field was modulated at 200 cps and its magnitude slowly varied. Under these conditions the signal output is proportional to the derivative of the absorption (d\ e " /dE).The experimental traces for an OH"" concentration of 3X10 16 OH~/cm 3 obtained at 1.3°K and a frequency of 35x 10 9 cps are shown in Figs. 1(a) and 1(b) for two orientations of the E field with respect to the crystalline direc-':^$^^i0^MMMi $'3?Wm^q CO (XL ;;^lpiit p©jfci|i#i| , •'&: Mi :: tfl.'£ MP î mi Tv.r f|E^^ Ww FIG, 1.Paraelectric resonance absorption from OH~ dipoles (3x 10 16 OH""/cm 3 ) in KC1 at i^ = 35.2x 10 9 cps and T = 1 0 3°K. In (a), E is along the [100] direction. Two resonances are clearly discernible. The relative intensities and linewidths are explained in the text. In (b), E is along the till] direction. The energy-level diagram giving rise to these transitions is shown in Fig. 2. 500

Electronic dipole resonance in smoky quartz

“…Recently various groups [12][13][14][15][16][17] investigated the ionic dipole resonance of centres in KC1, with experimental techniques that slightly differed from ours. We designed a re-entrant type microwave cavity, basically a piece of coaxial waveguide.…”

Electret Behavior and Ionic Thermal Currents in Alkali Halides

“…Ca Precipitation with OH in KC1.--The OH impurity is now one of the more important defects in the physics of alkali halides. Luty et al (12), Feher et al (13), and Kanzig et al (14) studied important paraelectric, paraelastic, and cooling effects of the OH dipole in alkali halides. Kuhn and Luty were the first to explain the apparent paradoxical behavior of the electrical conductivity of some of these solids as a function of temperature, by assuming a solid state reaction between Ca and OH ions.…”

Stage I Recovery of Deformed Platinum

“…Tunnelling has been reviewed by Hulett [48] and has recently been considered by Sussmann [49]. It has been observed experimentally by the paraelectric resonance of OHimpurity in alkali halides [50], and by acoustic loss in doped yttrium aluminium garnet [51] ; both expcrirnents show a temperature-independent relaxation time, which is attributed to tunnelling. Thc effect of zero-point motion on atomic jump rates has been discussed by Alefeld [52] and by Flynn [53] in terms of the dynamical rate theory, assuming that an atom jumps over a potential barrier when the sum of its phonon amplitudes exceeds a critical value.…”