EPR EVIDENCE OF EXTRINSIC SYMMETRY-BREAKING DEFECTS IN NOMINALLY PURE KTAO3

EPR measurements on nominally pure (undoped) KTaO3 single crystals at low temperature (4.2 K) are reported. Evidence is brought of impurity defects analyzed through the experimental spin-Hamiltonian parameters. Axial EPR spectra of Fe3+ in different cation positions are detected. An orthorhombic spectrum is found and attributed to Fe3+ substituting for K+ ions and involving nearby potassium vacancies as charge compensators. Manganese impurities are also observed following illumination of the sample to cause a change of the Mn valence state. © 1995 The American Physical Society.