Paramagnetic centers in chromium-doped Na$_{5}$AlF$_{2}$(PO$_{4})_{2}$ single crystal

The paramagnetic resonance of Na$_{5}$AlF$_{2}$(PO$_{4})_{2}$ single crystals with chromium impurity was studied. The Cr$^{3+}$ centers have been found to replace the triclinic Al$^{3+}$ 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.