LAUSR

The electron paramagnetic resonance (EPR) spectra of Gd3+ impurity centers in CaMoO4 single crystals have been investigated at temperatures T = 1.8, 4.2, and 99–300 K. The temperature dependences of the spin Hamiltonian parameters bnm(T) (n = 2, 4, m = 0, 4) have been determined, and their analysis has been carried out. The temperature contributions from the static lattice, b2(L) and b4m(L), to the spin Hamiltonian parameters bnm(T) have been separated. For this purpose, the changes of the static lattice contributions b2(L) and b4m(L) have been determined taking into account the temperature shifts of the oxygen ions nearest to the Gd3+ ions in CaMoO4 single crystals. The differences bnm(F) = bnm–bnm(L) have been attributed to the spin–phonon contribution. The analysis of the results obtained has demonstrated that the parameters b20(F) and b4m(F) are positive, and the dependence of b20(F) on the temperature T is well described in the model of local vibrations (G. Pfister). However, the temperature behavior of the parameter b4m(F) could not be described in the framework of the well-known models of the spin–phonon interaction.