Static, quasistatic, and quasidynamic Jahn-Teller effect in the EPR spectra of Ag/sup 2 +/ in SrO, CaO, and MgO

Journal Article · Fri Jul 01 00:00:00 EDT 1977 · Phys. Rev., B; (United States)

DOI:https://doi.org/10.1103/PhysRevB.16.86· OSTI ID:7209207

Boatner, L A; Reynolds, R W; Chen, Y; Abraham, M M

The EPR spectra observed for Ag/sup 2 +/ in the alkaline earth oxide host crystals SrO, CaO, and MgO provide an exceptionally clear example of the unusual spectral features associated with the transition from a static to a dynamic Jahn-Teller effect at low temperature. The spectrum observed for Ag/sup 2 +/ in SrO exhibits the low-temperature threefold tetragonal symmetry with symmetric line shapes and averaging at higher temperatures (80 to 200 K) which characterize the static Jahn-Teller (JT) effect. A complex line shape is observed at 1.3 K for Ag/sup 2 +/ in CaO with the orientation H parallel (111). These line-shape effects are due to a value of the ratio of random strain splitting delta-bar to ''tunneling'' splitting 3GAMMA which is intermediate to those associated with either the static or dynamic JT effect. The complex line shapes observed at 9 GHz with H parallel (111) have been computed by performing a numerical diagonalization of the matrix of strain and tunneling. From this calculation a value of 1.2 has been determined for the ratio delta-bar/3GAMMA. At a frequency of 23 GHz, the line shapes for Ag/sup 2 +/ in CaO exhibit additional effects due to the increased Zeeman interaction, and, by performing a simultaneous diagonalization of the strain, tunneling, and Zeeman matrices, it is possible to determine independently values of 4.7 and 3.9 cm/sup -1/ for delta-bar and 3GAMMA, respectively. For Ag/sup 2 +/ in MgO, the angular variation of the EPR spectrum at 1.3 K resembles the type of variation typical of a dynamic JT system, but with one component shifted and broadened by coupling via random strain to a nearly excited A/sub 2/ vibronic singlet level. A value of delta-bar/3GAMMA = 0.13 was determined for Ag/sup 2 +/ in MgO by fitting the observed angular variation to a computed angular variation derived from a numerical diagonalization of the matrix of strain and tunneling for the /sup 2/E-A/sub 2/ manifold.

• Research Organization: Ecole Polytechnique Federale de Lausanne, Laboratoire de Physique Experimentale, CH-1007 Lausanne, Switzerland
• OSTI ID: 7209207
• Journal Information: Phys. Rev., B; (United States), Vol. 16:1
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CALCIUM OXIDES
JAHN-TELLER EFFECT
MAGNESIUM OXIDES
SILVER IONS
ELECTRON SPIN RESONANCE
STRONTIUM OXIDES
GHZ RANGE 01-100
LINE WIDTHS
LOW TEMPERATURE
STRAINS
TEMPERATURE DEPENDENCE
TUNNEL EFFECT
ULTRALOW TEMPERATURE
VERY LOW TEMPERATURE
ZEEMAN EFFECT
ALKALINE EARTH METAL COMPOUNDS
ATOMIC IONS
CALCIUM COMPOUNDS
CHALCOGENIDES
CHARGED PARTICLES
FREQUENCY RANGE
GHZ RANGE
IONS
MAGNESIUM COMPOUNDS
MAGNETIC RESONANCE
OXIDES
OXYGEN COMPOUNDS
RESONANCE
STRONTIUM COMPOUNDS
360204* - Ceramics
Cermets
& Refractories- Physical Properties