ESR INVESTIGATIONS OF NOMINALLY PURE KTAO3

An ESR investigation of nominally pure KTaO3 was carried out at 4.2 < T < 77 K. Two new ESR spectra were observed. The first, with cubic sym metry, was shown to be that of Gd3+ substituted for K+. The analysis o f the spectrum line intensities and widths gave no evidence about Ta i ons displacements at low temperature. The second spectrum had axial sy mmetry and its source was identified as a new off-center impurity ion Fe+ substituted for K+ in KTaO3. The surrounding oxygen ion displaceme nts were shown to be the main reason for the Fe+ ESR spectra axiality. The possible origin of the pure KTaO3 low temperature anomalies is di scussed.