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In this paper, we combine synchrotron powder x-ray diffraction, 7 Li nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) experiments to study the structural evolution of Li 4 C 60 and how its electronic ground state depends on the crystal symmetry. The compound in the two-dimensional polymer phase with mixed interfullerene bonding motifs is a band gap insulator. EPR, however, reveals the presence of intrinsic centers originating from broken C 60–C 60 bonds and local Li off-stoichiometry that create states in the band gap and account for the complex temperature dependence of the spin susceptibility as well as the residual temperature dependence of the 7 Li NMR shift. At low temperatures, the Li+ ions are statically disordered on the 7 Li NMR timescale. The observed 7 Li NMR line narrowing at T> 200 K is ascribed to the Li+ diffusion dynamics and above room temperature the …
IOP Publishing
Publication date: 
1 Mar 2008

D Arčon, A Zorko, M Mazzani, M Belli, D Pontiroli, M Riccò, S Margadonna

Biblio References: 
Volume: 10 Issue: 3 Pages: 033021
New Journal of Physics