Abstract
We report experiments of electron spin resonance (ESR) of in polycrystalline samples of post-annealed in different atmospheres. After being synthesized by solid state reaction, pellets of were annealed for at under air, Ar or . Our temperature dependent ESR data revealed for all samples nearly temperature independent value (2.15(1)) and linewidth for . However, the values of ESR linewidth are strongly affected by the oxygen content in the sample. For instance, argon post-annealed samples show a much larger linewidth than the or air post-annealed samples. We attribute this broadening to an increase of the dipolar homogeneous broadening of the ESR lines due to the presence of oxygen vacancies which induce an spin inside the octahedra. Correlation between a systematic dependence of the ESR linewidth on the oxygen content and the high dielectric constant of these materials is addressed. Also, ESR, magnetic susceptibility, and specific heat data for a single crystal of and for polycrystals of are reported.
- Received 4 October 2005
DOI:https://doi.org/10.1103/PhysRevB.73.224404
©2006 American Physical Society