Electron paramagnetic resonance studies of cobalt and rare-earth impurity ions in YAlO3

The results of X-band electron paramagnetic resonance (EPR) measurements of Co2+ ions in YAlO3 (YAP) crystals in the temperature range 1.8-40 K are presented. The temperature and angular dependences of EPR spectra have been analysed using a triclinic spin Hamiltonian (SH) consisting of the electronic Zeeman and hyperfine terms. Two distinct positions D*a and D*b are identified for Co2+ complexes and ascribed to the substitutional Co2+ ions at the Al3+ and Y3+ sites, respectively. The values of the SH parameters are obtained by least squares fitting the D*a- and D*b-type Co2+ spectra yielding the principal (orthorhombic-like) values of the tensors g and A as well as the orientation of their principal axes. The additionally observed EPR spectra of the unintentional impurities Nd3+ and Er3+ in YAP crystals are also analysed.