ELECTRON PARAMAGNETIC RESONANCE OF Gd$sup 3+$ IN CaF$sub 2$, SrF$sub 2$, AND BaF$sub 2$

Journal Article · Tue Jan 01 04:00:00 EST 1963 · Helvetica Physica Acta (Switzerland)

OSTI ID:4148811

Sierro, J

Electron paramagnetic resonance (EPR) measurements at room temperature were made on trivalent gadolinium ions in single crystals of CaF/sub 2/, SrF/sub 2/, and BaF/sub 2/ and also in natural fluorites. The effects of heat treatments and of hydrolysis at high temperature on the EPR spectra were studied. In CaF/ sub 2/ there are four sets of spectra, the first having cubic symmetry, the second having axial symmetry about the cubic axes, and the two others having axial symmetry about the body diagonals of the cube. The spectra with cubic syrnmetry arise from Cd/sup 3+/ ions substituted for Ca/sup 2+/ ions without local charge compensation. The spectra with tetragonal symmetry are interpreted as resulting from Gd/sup 3+/ ions that have a charge compensating F/sup -/ ion occupying the nearest neighbor interstitial site. The spectra with trigonal symmetry arise from Gd/sup 3+/ ions that have an OH/sup -/ molecule ion or a charge compensating O/sup 2-/ ion occupying the site of one of the eight F/sup -/ ions surrounding the paramagnetic ion. In SrF/sub 2/ the results are very similar, except that a trigonal spectrum is present in the samples as grown. In BaF/sub 2/, only the cubic and the trigonal spectra are observed. The later is interpreted as arising from Gd/sup 3+/ ions substituted for divalent cations with a small displacement along one of the body diagonals of the cube. The deduced values of the pararneters in the usual spin Hamiltonian are given for the different spectra. The minimum temperature at which hydrolysis takes place was deterrnined to be about 500 deg C for CaF/sub 2/ and SrF/sub 2/ and about 600 deg C for BaF/sub 2/. In natural fluorites the spectra of Mn/sup 2+/ Eu/sup 2+/, and Gd/sup 3+/ in cubic symmetry and also Gd/sup 3+/ in tetragonal symmetry were observed. Furthermore, two spectra of color centers in relation with the natural color of some crystals were obtained. After x-ray irradiation some fluorites showed the spectra of the self-trapped hole center and that of atomic hydrogen. (auth)

• Research Organization: Universite, Geneva
• NSA Number: NSA-18-002417
• OSTI ID: 4148811
• Journal Information: Helvetica Physica Acta (Switzerland), Journal Name: Helvetica Physica Acta (Switzerland) Vol. Vol: 36; ISSN HPACA
• Country of Publication: Country unknown/Code not available
• Language: French

Related Subjects

ATOMS
BARIUM FLUORIDES
CALCIUM FLUORIDES
CATIONS
CONFIGURATION
CRYSTALS
DEFECTS
DIFFERENTIAL EQUATIONS
ELECTRIC CHARGES
ELECTRIC FIELDS
ELECTRONS
ENERGY
EUROPIUM
EXCITATION
FLUORITE
GADOLINIUM
HAMILTONIAN
HEAT TREATMENTS
HIGH TEMPERATURE
HYDROGEN
HYDROLYSIS
INTERACTIONS
IONS
IRRADIATION
LATTICES
LIFETIME
MAGNETISM
MANGANESE
MEASURED VALUES
MINERALS
MOLECULES
MONOCRYSTALS
PARAMAGNETISM
PHYSICS
QUADRUPOLES
RELAXATION
RESONANCE
SPECTRA
SPIN
STRONTIUM FLUORIDES
TEMPERATURE
ULTRASONICS
VIBRATIONS
X RADIATION