A new anticrossing region of monoisotopic impurity 53Cr ions in Y2SiO5

The monoisotopic impurity ions of 53 Cr in a single crystal of yttrium orthosilicate (Y 2 SiO 5 ) have been studied by the electron paramagnetic resonance (EPR). Several X-band EPR spin transitions of the chromium ion (S = 3/2) were recorded in magnetic fields up to 1.7 T. The chromium ion exhibited a substantial fine structure of spin sublevels, with two doublets split by 53 GHz. As a consequence of the high anisotropy of the zero-field interactions, the resonance conditions of the EPR transitions are strongly dependent on the direction of the external magnetic field relative to the crystallographic axes. In some orientations, the nonlinear dependence of the spin sublevels on the magnetic field leads to the formation of an anticrossing between spin states with projections m S = + 1 / 2 and m S = - 3 / 2 . In addition to this well established anticrossing region, a new region formed by the states with projections m S = - 1 / 2 and m S = - 3 / 2 has been identified. It appears near the upper limit of the EPR spectrometer (1.7 T), where the core of the spectrometer magnet approaches saturation. The EPR spectra of the scandium endofullerene Sc 2 @C 80 (CH 2 Ph) are taken as a standard to calibrate the magnetic field in this regime. This procedure enables a more accurate determination of the fine structure of the chromium ion. The values D = 25.07 GHz and E = 5.29 GHz are derived by comparing calibrated experimental data with numerical simulations.