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RESEARCH PRODUCT

Electron paramagnetic resonance study of theCe3+pair centers inYAlO3:Ce scintillator crystals

E. MihokovaV. V. LagutaPavel NovákMartin NiklMaksym Buryi

subject

PhysicsCoupling constantExchange interactionLattice (group)02 engineering and technology021001 nanoscience & nanotechnologyCondensed Matter Physics01 natural sciencesSpectral lineElectronic Optical and Magnetic Materialslaw.inventionNuclear magnetic resonancelaw0103 physical sciencesDensity functional theoryAtomic physics010306 general physics0210 nano-technologyElectron paramagnetic resonanceEnergy (signal processing)Spin-½

description

Single crystals of $\mathrm{YAl}{\mathrm{O}}_{3}$ doped with Ce have been studied by electron paramagnetic resonance (EPR) at the 9.4 and 34 GHz microwave bands. Besides the single-ion $\mathrm{C}{\mathrm{e}}^{3+}$ spectrum, measurements have revealed many satellite lines which belong to the $\mathrm{C}{\mathrm{e}}^{3+}\text{\ensuremath{-}}\mathrm{C}{\mathrm{e}}^{3+}$ pair centers. Their spectra have been fitted by a general effective spin Hamiltonian describing two interacting particles with the spin $S=1/2$. Corresponding $g$ factors and spin-spin coupling constants have been determined. The spin-spin coupling constants are in the range from 0.1 up to $0.65\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{\ensuremath{-}1}$ for the nearest and next-nearest neighbors depending on the distance between Ce ions and their position. The exchange interaction between next-nearest neighbors (NNNs) is comparable to or even bigger than that between nearest neighbors (NNs), being in the range $0.4\ensuremath{-}0.6\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{\ensuremath{-}1}$. For a single $\mathrm{C}{\mathrm{e}}^{3+}$ ion, crystal field parameters, energy sublevels of the ${}^{2}{F}_{5/2}$ and ${}^{2}{F}_{7/2}$ multiplets and principal $g$ tensor components were obtained from the density functional theory calculation. They are in satisfactory agreement with those determined experimentally. The principal $g$ tensor components of $\mathrm{C}{\mathrm{e}}^{3+}$ pair centers are also calculated. Nevertheless, it was impossible to assign each of the satellite lines to actual positions of the six NN and 12 NNN Ce pairs in the lattice due to lack of valid information on the sign of the exchange interactions. The influence of $\mathrm{C}{\mathrm{e}}^{3+}$ pairs on the luminescence efficiency is discussed as well.

https://doi.org/10.1103/physrevb.92.224105