13C NMR study of the magnetic properties of the quasi-one-dimensional conductor, (TMTTF)2SbF6

Abstract

Magnetic properties in the quasi-one-dimensional organic salt (TMTTF)2SbF6 are investigated by 13 C NMR under pressures. Antiferromagnetic phase transition at ambient pressure (AFI) is confirmed. Charge-ordering is suppressed by pressure and is not observed under 8 kbar. For 5 < P < 20 kbar, a sharp spectrum and the rapid decrease of the spin-lattice relaxation rate 1/T1 were observed below about 4 K, attributed to a spin-gap transition. Above 20 kbar, extremely broadened spectrum and critical increase of 1/T1 were observed. This indicates that the system enters into another antiferromagnetic phase (AFII) under pressure. The slope of the antiferromagnetic phase transition temperature TAFII, dTAFII/dP , is positive, while TAFI decreases with pressure. The magnetic moment is weakly incommensurate with the lattice at 30 kbar.