EPR spectroscopic characterization of Gd/sup 3 +/ in the monazite-type rare-earth orthophosphates: LaPO/sub 4/, CePO/sub 4/, PrPO/sub 4/, NdPO/sub 4/, SmPO/sub 4/, and EuPO/sub 4/
The mineral monazite, a mixed lanthanide orthophosphate LnPO/sub 4/, is considered as a perfect host for geologic disposal of actinides, rare earths, and possibly other elements formed during nuclear-reactor operation. Synthetic monazite-type orthophosphates of all the elements of the first half of the lanthanide series (except Pm) have been prepared: single crystals were grown using a flux technique, and powders were precipitated in molten urea. The electron paramagnetic resonance (EPR) spectra of intentionally added Gd impurities show that the Gd/sup 3 +/ ions occupy predominantly substitutional rare-earth sites in both the flux-grown single crystals and the precipitated powders. Though these sites have a very low (triclinic C/sub 1/) symmetry, the spectra were successfully interpreted using an orthorhombic spin Hamiltonian. It has been found that, while the main spin-Hamiltonian parameter b/sup 0//sub 2/ is almost constant when going from the LaPO/sub 4/ to the EuPO/sub 4/ host (b/sup 0//sub 2/approx. =+830 x 10/sup -4/ cm/sup -1/), the parameter b/sup 2//sub 2/ decreases monotonically from +373 x 10/sup -4/ to +283 x 10/sup -4/ cm/sup -1/, respectively. The complete analysis (i.e., angular variations of the EPR lines and position of the principal electric-field axes relative to the crystallographic axes) of the EPR single-crystal spectra has been done for the two diamagnetic hosts LaPO/sub 4/ and EuPO/sub 4/, where the observed EPR lines are the sharpest. It is shown, in particular, that the two magnetically inequivalent EPR spectra (i.e., 14 lines) observed for the monazite-type single crystals are in fact equivalent when the magnetic field is applied parallel or perpendicular to the b axis of the monoclinic structure (i.e., for these directions, only seven degenerate lines are observed). These results are in perfect agreement with the description of the monazite structure.
- Research Organization:
- Solid State Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830
- DOE Contract Number:
- W-7405-ENG-26
- OSTI ID:
- 6685912
- Journal Information:
- Phys. Rev. B: Condens. Matter; (United States), Journal Name: Phys. Rev. B: Condens. Matter; (United States) Vol. 23:3; ISSN PRBMD
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360602* -- Other Materials-- Structure & Phase Studies
360603 -- Materials-- Properties
ACTINIDE COMPOUNDS
ALPHA PARTICLES
ANGULAR MOMENTUM
CERIUM COMPOUNDS
CERIUM PHOSPHATES
CHARGED PARTICLES
CRYSTAL STRUCTURE
CRYSTALS
DATA
ELECTRON SPIN RESONANCE
ELEMENTS
EUROPIUM
EXPERIMENTAL DATA
GADOLINIUM
HAMILTONIANS
IMPURITIES
INFORMATION
LANTHANUM COMPOUNDS
LANTHANUM PHOSPHATES
MAGNETIC RESONANCE
MANAGEMENT
MATERIALS
MATHEMATICAL OPERATORS
METALS
MINERALS
MONAZITES
MONOCRYSTALS
NEODYMIUM COMPOUNDS
NEODYMIUM PHOSPHATES
NUMERICAL DATA
OXYGEN COMPOUNDS
PARTICLE PROPERTIES
PHOSPHATES
PHOSPHORUS COMPOUNDS
POWDERS
PRASEODYMIUM COMPOUNDS
PRASEODYMIUM PHOSPHATES
QUANTUM OPERATORS
RADIATION EFFECTS
RADIOACTIVE MATERIALS
RADIOACTIVE MINERALS
RADIOACTIVE WASTE STORAGE
RARE EARTH COMPOUNDS
RARE EARTHS
RESONANCE
SAMARIUM
SPIN
STORAGE
THORIUM COMPOUNDS
THORIUM MINERALS
THORIUM PHOSPHATES
WASTE MANAGEMENT
WASTE STORAGE