EPR Study of Cr3+ and Fe3+ Impurity Ions in Nominally Pure and Co2+-Doped YAlO3 Single Crystals

Abstract

In this paper, we report electron paramagnetic resonance (EPR) measurements of YAlO3 (YAP) single crystals and their preliminary theoretical analysis. Two kinds of the as-grown and annealed (in reducing N2 plus H2 atmosphere at 1100 K) YAP samples, nominally pure and doped with Co2+ ions, were studied. The presence of small amounts of Cr3+ and Fe3+ paramagnetic centers is revealed from the observed EPR spectral lines. In the annealed crystals, a decrease in the line intensity for Fe3+ ions and a simultaneous increase for Cr3+ ions is observed. Interestingly, a gradual decrease in intensity of both the Cr3+ and Fe3+ lines down to zero has been observed in EPR spectra below 80 K. The aim of this paper, first in the series of investigations, is to unravel characteristics of unintentional impurities present in nominally pure YAP crystals as indicated by EPR measurements. For this purpose, the spin Hamiltonian analysis of EPR spectra has been carried out on the basis of the triclinic (C i ) site symmetry. The fitted spin Hamiltonian parameters for Cr3+ and Fe3+ ions, i.e., zero-field splitting parameters and the Zeeman electronic tensor components, agree well with literature data. More detailed analysis of low symmetry aspects involved in EPR studies based on superposition model will be provided elsewhere.