Representative glass series of different vanadium content and valence state have been studied with special emphasis on V4+-V4+ spin-spin interaction. From temperature dependent EPR studies paramagnetic Curie temperatures and J values have been determined. We demonstrate that this method is informative in the whole glass formation range. It is shown that there is an antiferromagnetic → ferromagnetic transition at c = V4+/(V4+ + V5+) ∼ 0.17 (2.3×1021 spin cm-3). At this composition the glass is essentially homogeneous and displays maximal conductivity. In glasses of higher V4+ content, in which the dominating interaction is ferromagnetic, the conductivity gradually decreases. Therefore, ferromagnetically coupled V4+ - V4+ pairs seem to contribute to conductivity less effectively.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Ceramics and Composites
- Condensed Matter Physics
- Materials Chemistry