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Impurity centers
Temperature dependences of the parameters of the initial splitting of Gd$^{3+}$ in CaMoO$_{4}$ (lattice and spin–phonon contributions)
A. D. Gorlov Institute of Natural Sciences, Ural Federal University, Ekaterinburg
Abstract:
The electron paramagnetic resonance (EPR) spectra of Gd
$^{3+}$ impurity centers in CaMoO
$_{4}$ single crystals have been investigated at temperatures
$T$ = 1.8, 4.2, and 99–300 K. The temperature dependences of the spin Hamiltonian parameters
$b_{n}^{m}(T)$ (
$n$ = 2, 4,
$m$ = 0, 4) have been determined, and their analysis has been carried out. The temperature contributions from the static lattice,
$b_{2}$(L) and
$b_{4m}$(L), to the spin Hamiltonian parameters
$b_{n}^{m}(T)$ have been separated. For this purpose, the changes of the static lattice contributions
$b_{2}$(L) and
$b_{4m}$(L) have been determined taking into account the temperature shifts of the oxygen ions nearest to the Gd
$^{3+}$ ions in CaMoO
$_{4}$ single crystals. The differences
$b_{nm}(F) =b_{n}^{m}-b_{nm}$(L) have been attributed to the spin–phonon contribution. The analysis of the results obtained has demonstrated that the parameters
$b_{20}(F)$ and
$b_{4m}(F)$ are positive, and the dependence of
$b_{20}(F)$ on the temperature
$T$ is well described in the model of local vibrations (G. Pfister). However, the temperature behavior of the parameter
$b_{4m}(F)$ could not be described in the framework of the well-known models of the spin–phonon interaction.
Received: 26.04.2016
Revised: 09.09.2016
DOI:
10.21883/FTT.2017.03.44170.157
Fulltext:
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