Mikhail Eremin

The effect of nanosecond magnetic pulses on a photon echo signal in the Er³⁺-doped YLiF₄ and LuLiF₄ samples has been considered. A strong dependence of the photon echo intensity on the parameters of the magnetic pulse and the direction of variation of the external magnetic field H has been found. The application of magnetic pulses can increase the echo intensity by a factor of 5–6. The irreversibility (nonreciprocity) effect is explained by the occurrence of the spatial dispersion of the permittivity.

In LiYF₄ single crystal doped by Er ions, the effect of changing the intensity of electron paramagnetic resonance signals under the reversal of the magnetic field direction (nonreciprocity) has been detected. The effect is attributed to interference between the magnetic and electric dipole transitions. Electric dipole transitions are caused by mixing of electronic configurations of the Er³⁺ ion under effect of the odd type crystal field acting on electrons of erbium. As a result, the probability of such transitions turns out to be comparable to the probability of magnetic dipole transitions. The obtained dependence of the interference effects on the direction of the applied magnetic field is well reproduced by the quantum-mechanical calculations.

В работе рассматривается влияние импульсов магнитного поля наносекундной длительности на сигнал фотонного эха в образцах YLiF и LuLiF, активированных ионами Er. Обнаружена сильная зависимость интенсивности фотонного эха от параметров магнитного импульса и направления изменения внешнего магнитного поля H. При включении магнитных импульсов интенсивность эха может возрастать в 5–6 раз. Эффект необратимости (невзаимности) объясняется возникновением пространственной дисперсии диэлектрической проницаемости.

The effective Hamiltonians of the fine structure of Fe2+ (5D) terms are derived using the methods of operator perturbation theory taking into account covalent bonds between iron and oxygen ions. The energy operators of coupling of magnetic and electric dipole moments with the electric field are obtained for states of multiplets Fe2+ (5E) and Fe2+ (5T2) with minimal sets of parameters. The energy spectra of low-lying states, the magnetic anisotropy parameters, and the distribution of quadrupole and induced electric dipole moments over all positions in the unit cell are calculated. The results of calculations are compared with available experimental data.

The effective Hamiltonians of the fine structure of Fe²⁺ (⁵D) terms are derived using the methods of operator perturbation theory taking into account covalent bonds between iron and oxygen ions. The energy operators of coupling of magnetic and electric dipole moments with the electric field are obtained for states of multiplets Fe²⁺ (⁵E) and Fe²⁺ (⁵T₂) with minimal sets of parameters. The energy spectra of low-lying states, the magnetic anisotropy parameters, and the distribution of quadrupole and induced electric dipole moments over all positions in the unit cell are calculated. The results of calculations are compared with available experimental data.