EPR spectroscopy of 53Cr monoisotopic impurity ions in a single crystal of yttrium orthosilicate Y2SiO5

The electron paramagnetic resonance spectra of 53Cr monoisotopic impurity ions in yttrium orthosilicate single crystals (Y2SiO5) were studied by electron paramagnetic resonance (EPR) in the X-band. The directions of the principal magnetic axes and the parameters of the effective spin Hamiltonian, which describes magnetic characteristics of the impurity centers of chromium are determined. It is shown that the orientation dependencies of the EPR spectra are described by the second-order spin Hamiltonian corresponding to the rhombic symmetry of the local crystal field acting on the impurity ion. It was assumed that the g-tensor and A-tensor describing the Zeeman energy of electron levels in a magnetic field and the hyperfine interaction of electron and nuclear spins are isotropic, and the entire anisotropy of the EPR spectra is due to the anisotropy of the D-tensor, which describes the fine structure of electron levels in crystal electric field. A strong dependence of the probability of forbidden transitions between hyperfine sublevels of electron levels on the orientation of an external magnetic field is established. Moreover, for some orientations, the probability of forbidden transitions becomes comparable to the probability of allowed transitions.