Determining Electron Spin-Transfer Mechanisms in Paramagnetic Ba2YMO6 (M = Mo, Re, Ru) Double Perovskites by 89Y and 137Ba MAS NMR Spectroscopy
journal contributionposted on 08.11.2012, 00:00 by Vladimir K. Michaelis, Brandon J. Greer, Tomoko Aharen, John E. Greedan, Scott Kroeker
The spin-transfer mechanisms of three B-site ordered double perovskites, Ba2YMO6 (M = Mo, Re, and Ru), were determined using variable-temperature 89Y and 137Ba magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. On the basis of symmetry-compatible overlap and trends observed in the MAS NMR, spin polarization was determined to be the dominant mechanism at the Y sites and spin delocalization to be the operative mechanism at the Ba sites. The MAS NMR spectra display 89Y and 137Ba chemical shifts that far exceed those of other paramagnetic solids, appearing at up to −6402 and +12 200 ppm, respectively. Detection of additional resonances in 89Y MAS NMR indicates a small degree of cation site mixing in two cases.