Electron spin resonance investigation of Mn2+ ions and their dynamics in Mn-doped SrTiO3

A. Tkach,
P. M. Vilarinho,
L. Jastrabik

I. M. Frantsevich Institute for Problems of Materials Science of the NAS of Ukraine, Omeliana Pritsaka str.,3, Kyiv, 03142, Ukraine
Physical Review B - Maryland, USA: American Physical Society (APS), 2007, #76


Using electron spin resonance (ESR), the lattice position and dynamic properties of Mn2+ ions were studied in 0.5 and 2 at. % manganese-doped SrTiO3 ceramics prepared by the conventional mixed oxide method. The measurements show that Mn2+ ions preferably (up to 97%) substitute for the Sr if the ceramics are prepared with a deficit of Sr ions. Motional narrowing of the Mn2+ ESR spectrum was observed when the temperature increased from 120  to 240–250 K, which was explained as a manifestation of the off-center position of this ion at the Sr site. From the analysis of the ESR spectra, the activation energy Ea=86 mV and frequency factor 10≈(1–5)1013 s-1 for the jumping of the impurity between symmetrical off-center positions were determined. Both are in agreement with those previously derived from the dielectric relaxation. This proves that the origin of the dielectric anomaly in SrTiO3:Mn is produced by the reorientation dynamics of Mn2+ dipoles.