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

• A new anticrossing region of spin sublevels (m S = −1/2 and m S = −3/2) of monoisotopic 53 Cr ions doped in a single Y 2 SiO 5 crystal is found. • The rotation of the crystal with respect to the magnetic field axis allows for the observation of two anticrossing regions in the EPR spectra. • The endofullerene Sc 2 @C 80 (CH 2 Ph) spectrum is used as a standard for magnetic field recalibration near the saturation mode of the spectrometer. • The numerical calculations reproduce well the angular dependence of the EPR spectra over a wide range of magnetic fields. • The fine structure parameters have been adjusted from the comparison of the experimental data with the numerical calculations. 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.