Magneto-electric spin resonance of Cu 2+ dimer associate in BaF 2 single crystal

Abstract The unusual resonance lines were observed in continuous wave electron paramagnetic resonance spectra of dimer associate of Cu2+ ions in BaF2 single crystal. The phase of these lines was significantly shifted from the phase of magnetic field modulation. We associate the appearance of these lines with special features of the high-spin electron systems under resonance interaction with microwave electromagnetic field. We take in to account that under resonance excitation of the high-spin electron spin magnetic dipole orientation transforms to quadrupole alignment, and there is the reversible mutual transformation of the dipole and quadrupole degrees of freedom. Simultaneous excitation of magnetic dipole and electric quadrupole resonance transitions in a dielectric resonator of an electron paramagnetic resonance spectrometer results in appearance of the phase shifted resonance lines.