Wide-band EPR spectroscopy of YAlO$_3$ : Tm$^{3+}$ single crystals

The YAlO$_3$ : Tm$^{3+}$ single crystal has been studied on a wide-band EPR spectrometer. The EPR spectra of Tm$^{3+}$ ions in the frequency range of 90–160 GHz have been detected for the first time. It has been confirmed that thulium ions substitute the position of Y$^{3+}$ in the crystal lattice. The detected spectra have been described with the use of a spin Hamiltonian with the effective spin $S$ = 1/2. A comparative analysis of the orientation of the magnetic axes of the Tm$^{3+}$ paramagnetic center with earlier data on other rare-earth ions has been performed.