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A new off‐center defect system, RbCl:Li + , studied with dielectric techniques under hydrostatic pressure
Author(s) -
Thörmer K.,
Lüty F.
Publication year - 1978
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2220900130
Subject(s) - dielectric , hydrostatic pressure , dipole , condensed matter physics , debye , relaxation (psychology) , chemistry , doping , materials science , thermodynamics , physics , psychology , social psychology , optoelectronics , organic chemistry
RbCl crystals with Li + doping, spanning a concentration range of nearly three orders of magnitude, are systematically studied in their real and imaginary dielectric response under hydrostatic pressure (up to 7 kbar). A dielectric constant anomaly and loss peak around 40 K is found, which can be fitted to a Langevin‐Debye behavior of classical dipoles with an activation energy for reorientation of 510 K. For small Li + doping ( N < 10 18 cm −3 ), this dielectric response scales with the Li + concentration, yielding (for Lorentz corrected fields) a dipole moment of 〈 p 〉 = 0.52 e Å. The potential barrier for the Li + dipole reorientation is found to be drastically reduced under hydrostatic pressure, shifting the observable relaxation to low temperatures. Though this pressure tuning process is interrupted by the NaCl → CsCl structural phase‐transition at 4.6 kbar, it can be extrapolated that for about 8 kbar (i.e., 2% compression) RbCl:Li + should become a tunneling system similar to KCl:Li + . Consequences of the observed behavior for the theoretical understanding and host‐lattice trends of Li + off‐center defects and for the behavior of F A (Li) centers are discussed.