Distribution of Cobalt Co2+ Ions in Single Crystals of Spinel Li0.5Ga2.5O4
https://doi.org/10.1134/S0031918X23602883
The distribution of Co2+ ions over sublattices and structurally nonequivalent positions in the unit cell of the crystal lattice of a single crystal of lithium gallium spinel Li0.5Ga2.5O4 is shown. This distribution determines the properties of both mono- and nanocrystalline substances. The distribution is obtained by a special technology and is manifested in the electron paramagnetic resonance (EPR) spectra. The distribution of Co2+ ions depends on the structural and magnetic nonequivalence. The structural and magnetic nonequivalence causes a multiminimum behavior of the crystal field potential in the unit cells of single crystals at the locations of Co2+ ions. The Co2+ ions are found in complexes with tetrahedral and octahedral oxygen ions. Three types of EPR spectra of Co2+ ions have been found and investigated. The [Math Processing Error]Cotetr2+ spectrum is attributed to the Co2+ ion, which replaces the Ga3+ ion located in a tetrahedral oxygen environment. The spectrum of the [Math Processing Error]Cooct2+ ion located in the crystal field with axial symmetry belongs to the Co2+ ion replacing the Li+ ion located in an octahedral oxygen environment. The spectrum of the [Math Processing Error]Cooct2+ ion located in a low symmetry crystal field belongs to the Co2+ ion replacing the Ga3+ ion located in an octahedral oxygen environment. The nearest cationic environment of the ion creates rhombic distortions due to the different valence numbers of Li+ and Ga3+. The results of studying the angular dependences of the spectra show the presence of four and twelve magnetically nonequivalent positions in the unit cells.