Manifestation of interionic interaction in the optical spectra of LiTbF4

Spectra of optical absorption and luminescence of LiTbF4 crystal in the region of head lines of 7Fj-5D4 transitions were investigated in 1.35-20 K range, applying external magnetic field of 0-25 kOe intensity. Splitting of Tb3+ ion ground state, conditioned by internal field of ferromagnetic phase was noted in absorption spectra, measured at T<Ts = 2.87 K and the temperature dynamics of phase transformation was followed. Experimental results were used to determine the values of saturation magnetization of crystal Mo (1.1+-0.1)kOe and internal field parameter λ = 5.8+-0.5. Manifestations of exciton state existence in the crystal were noted: the difference in splitting values, measured according to transitions to different singlet states, and the presence of effective luminescence sensitization of defect centers