Effect of Magnetoelectric Nonreciprocity in the Submillimeter EPR Spectroscopy of LiYF4 Doped by 166Er3+ Ions

In LiYF 4 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 Er 3+ 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.