The paramagnetic resonance of Na5AlF2(PO4)2 single crystals with chromium impurity was studied. The Cr3+ centers have been found to replace the triclinic Al3+ positions. In the local coordinate system, the spectra of these centers were described by the spin Hamiltonian of rhombic symmetry. In addition, vanadium centers and unidentified triclinic symmetry centers have been observed.

The EPR spectrum of yttrium and scandium silicate single crystals doped with chromium has been studied at various frequencies. Y_2SiO_5 has one triclinic Cr^3+ center, while the Sc_2SiO_5 crystals demonstrate two nonequivalent centers. The spin Hamiltonian parameters of these centers have been determined. These centers are found to be tricharged chromium ions localized in the yttrium and scandium positions.

В рамках суперпозиционной модели для начального расщепления основного состояния проведен анализ параметров спинового гамильтониана второго ранга ромбических центров Gd3+ и Eu2+ в иттрий-алюминиевом гранате. Показано, что описание экспериментальных данных в этой модели возможно только при допущении релаксации лигандного окружения парамагнитной примеси. Работа выполнена в рамках государственного задания Минобрнауки РФ для Уральского федерального университета. Измерения проведены на спектрометре Центра коллективного пользования "Современные нанотехнологии" Уральского федерального университета. DOI: 10.21883/FTT.2017.05.44384.286

In the Li2CaSiO4 crystal, in addition to intense axial centers of Cr4+, the EPR spectra of impurity ions Mn2+ (S = 5/2), Gd3+ (S = 7/2), and Cu2+ (S = 1/2) have been discovered and studied. Manganese and gadolinium ions exhibit spectra of tetragonal symmetry, copper ions are represented by spectra of both axial and triclinic symmetry. The parameters of the spin Hamiltonians of tetragonal centers are determined. It was shown that Mn2+ and Gd3+ ions substitute for calcium ions with an eightfold oxygen environment, copper ions are localized in lithium positions with a tetrahedral environment. The reasons for the appearance of Cu2+ triclinic centers are discussed.

In specially grown single crystals of yttrium-aluminum garnet, the orthorhombic centers 153Eu2+ and 151Eu2+ were investigated. The parameters of hyperfine and quadrupole interactions, which describe the hyperfine structure of the EPR spectrum of both isotopes, are determined.