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

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

Інститут проблем матеріалознавства ім. І. М. Францевича НАН України , вул. Кржижановського 3, Київ, 03142, Україна
Physical Review B - Maryland, USA: Американське Фізичне Суспільство (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.