Electric Field Effect in ESR Spectra of Fe³⁺ and Mn⁴⁺ Centers in Thin SrTiO<inf>3</inf> Plates

Abstract

Abstract: The electric field effect in electron spin resonance spectra of Fe3+ and Mn4+ impurity ions in thin oriented single-crystal plates of strontium titanate has been studied; the crystal structure of these samples at T > 105 K is tetragonal (i.e., differs from both cubic and antiferrodistortive tetragonal structure that is inherent in SrTiO3 at T < 105 K). It is shown that the electric field effects for the investigated centers are quadratic with respect to the applied field and have identical signs and orders of magnitude, thus indicating a nonpolar character of the observed high-temperature tetragonal state. An analysis of the dependences of the axiality value on the applied field indicates that the electric field effect is not related to electrostriction and caused by modification of the wave function of the ground state of impurity centers.