Paramagnetic resonance of Cr³⁺ in kyanite

The spin resonance spectra of Cr³⁺ ions in triclinic kyanite Al₂SiO₅ can be interpreted with a spin Hamiltonian containing axial and rhombic terms. There are three magnetically inequivalent sites whose principal magnetic axes are nearly in the (100) crystal plane at angles of approximately -40°, +30°, +50° to the c axis. The measured parameters are g_|| = 1.982 ± 0.0005, g_⊥ = 1.977 ± 0.002 and |D| = 19.07, 20.85, 15.97 Gc/s; E = 0.54, 1.49, 1.04, Gc/s for the three ions. The inequivalent sites are correlated with the possible substitutional sites available in the crystal.