On 80th anniversary of Vadym Loktev

Alexander Davydov, and his first research was focused on the photoconductivity of molecular crystals with strong electron-phonon interaction.In general, Vadym Loktev's field of activity covers solidstate theory, in particular, the theory of cryocrystals, magnetic phenomena in solids, disordered systems, and the theory of superconductivity with a special emphasis on the high-temperature superconductivity.Prof. Loktev suggested a new approach to describing the magnetic crystals with strong single-ion anisotropy, predicted phenomena of biexciton splitting and polarization of spectral lines in the two-particle light absorption region, and a new field-dependent linear magneto-optic effect.He developed a consistent quantitative theory of the absorption spectra of solid phases of oxygen and predicted a non-collinear magnetic structure for one of its low-temperature phases.He also constructed a theory of magnetic impurity systems, in which the local level is located near the edge of the spin-wave zone.Later, he contributed to the Ivanov-Loktev-Pogorelov theory, which predicted anomalous enhancement of infrared absorption in