Paramagnetic resonance studies of crystals with disorder
Materials which are expected to display some of the properties intrinsic to amorphous insulators are examined using electron paramagnetic resonance techniques. Electron spin-lattice relaxation probes the dynamic structure of a material, and hence can be used to probe the Localized Tunneling States (LTS) believed to be responsible for the anomalous low temperature thermal properties of glasses. The crystal system lithium doped calcium oxide is known to have a paramagnetic center adjacent to a lithium substitutional impurity. This impurity may give rise to LTS similar to those observed in glasses. The electron spin-lattice relaxation rate of this center is measured as a function of temperature, frequency, crystal orientation, and nuclear spin state. The result cannot be explained using the conventional phonon theory of relaxation of color centers. A theory is developed which postulates that the center relaxes by mutual transitions of the electron spin and an adjacent LTS, coupled with the emission or absorption of a phonon. The electron spin- nuclear spin hyperfine interaction provides the coupling between the electron and the tunneling lithium.
- Research Organization:
- Illinois Univ., Urbana (USA). Dept. of Physics
- DOE Contract Number:
- AC02-76ER01198
- OSTI ID:
- 5013518
- Report Number(s):
- DOE/ER/01198-1370; ON: DE82005970
- Country of Publication:
- United States
- Language:
- English
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75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALKALINE EARTH METAL COMPOUNDS
ALLOYS
CALCIUM COMPOUNDS
CALCIUM OXIDES
CHALCOGENIDES
CRYSTAL LATTICES
CRYSTAL STRUCTURE
DATA
ELECTRON SPIN RESONANCE
ENDOR
HYPERFINE STRUCTURE
INFORMATION
LITHIUM ADDITIONS
LITHIUM ALLOYS
MAGNETIC RESONANCE
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
RELAXATION
RESONANCE
SPIN-LATTICE RELAXATION
THEORETICAL DATA
TUNNEL EFFECT