Paramagnetic centers of Mn$^{2+}$, and Gd$^{3+}$ и Cu$^{2+}$ in single crystal of Li$_{2}$CaSiO$_{4}$ doped with chromium

In the Li$_{2}$CaSiO$_{4}$ crystal, in addition to intense axial centers of Cr$^{4+}$, the EPR spectra of impurity ions Mn$^{2+}$ ($S$ = 5/2), Gd$^{3+}$ ($S$ = 7/2), and Cu$^{2+}$ ($S$ = 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 Mn$^{2+}$ and Gd$^{3+}$ 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 Cu$^{2+}$ triclinic centers are discussed.