Abstract:
A YAlO$_3$:Ho(0.15 at) crystal has been studied by tunable broadband EPR spectroscopy in the subterahertz range.%). The measured spectra of holmium ions with a resolved ultrathin structure correspond to resonant transitions between the electron-nuclear sublevels of the main and first excited singlets of the main multiplet $^5$I$_8$ of No$^{3+}$ ions split in a crystal field with symmetry, replacing Y$^{3+}$ ions in two magnetically unequal positions. EPR spectra of Ho$^{3+}$–Ho$^{3+}$ dimers containing nearby holmium ions in magnetically equivalent positions have also been recorded. Within the framework of the exchange charge model, the parameters of the crystal field are obtained and calculations of Stark splits, ultrathin structure constants, $g$ factors of the isolated center and dimer are performed, which are compared with the optical spectroscopy data presented in the literature and with the experimental results of this work. The effectiveness of the theoretical model was verified by calculating the characteristics of the previously studied YAlO$_3$:Tm crystal.
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