Kf. Thier et M. Mehring, C-13 NMR-STUDY OF THE METAL-INSULATOR AND STRUCTURAL PHASE-TRANSITIONIN THE ORGANIC CONDUCTOR (FLUORANTHENYL)2PF6, Physical review. B, Condensed matter, 50(4), 1994, pp. 2142-2149
C-13 NMR measurements on single crystals of (fluoranthenyl)2PF6 at var
iable temperatures and for different orientations of the crystals with
respect to the external field reveal strongly temperature-dependent K
night-shift anisotropies. Hyperfine-interaction tensors for the differ
ent carton sites of the fluoranthene molecule were determined and are
compared with molecular-orbital-type calculations. The temperature dep
endence of the paramagnetic spin susceptibility was determined through
the metal-insulator transition. The spectra exhibit clearly a structu
ral, as well as a metal-insulator, phase transition at and below 200 K
. A detailed analysis of the temperature-dependent shift data leads to
the determination of the temperature-dependent order parameter for bo
th transitions.