Spin-density-wave state in(TMTSF)2PF6: A

S. Valfells

¹

,

P. L. Kuhns

²

,

Alfred Kleinhammes

³

et al.

Abstract

We present a nuclear magnetic resonance study of the low-temperature spin-density-wave ͑SDW͒ ground state in the quasi-one-dimensional conductor ͑TMTSF͒ 2 PF 6 ͓bis-͑tetramethyl-tetraselenafulval-ene͒hexafluorophosphate͔. Using magnetic fields up to 22 T, we have measured the 77 Se spin-lattice (T 1 Ϫ1 ) andspin-spin relaxation rates (T 2 Ϫ1 ) above and below the SDW transition (T SDW Ϸ12 K͒. Between T SDW and Ϸ4 K, we observe anomalously fast and Korringa-like T 1 Ϫ1 ; below 4 K, T 1 Ϫ1 decays rapidly. A reduction in T 2 Ϫ1 is also observed at 4 K, but the absorption linewidth does not change to within experimental error. We attribute this behavior to an incomplete SDW transition at T SDW , leaving residual carriers at the Fermi level, and a subsequent consummation of the transition at 4 K. Our data below 4 K are consistent with a simple model of the temperature dependence of T 1 Ϫ1 in a fully gapped and low-dimensional conductor.

Anisotropic electronic and magnetic properties of the quasi-two-dimensional heavy-fermion antiferromagnetCeRhIn5

“…10,[23][24][25] For one of these materials, it was determined that a gap opens in the electronic spectrum at the SDW transition temperature as determined from NMR measurements which display activated Korringa-like behavior for TϽT SDW . 26 These results along with the analysis of the specific heat data point to CeRhIn 5 as having a gapped Fermi surface due to the formation of an anisotropic SDW.…”

Solid-state selenium-77 NMR

“…Selenium-77 has become the preferred nucleus of interest in these solid-state NMR studies, as the selenium nuclei are relatively rigid within the TMTSF framework and analysis of the electronic origin of the 77 Se relaxation rates in comparison to those obtained over a wide temperature range via 1 H NMR is simplified [133,134]. Selenium-77 nuclear spin-lattice relaxation rates, T À1 1 , are the most common form of NMR information utilized in characterization of the phase transitions in (TMTSF) 2 X salts, as they reveal low-frequency electronic spin dynamics occurring at or near the onset of these phase transitions [135].…”

13C NMR study of commensurate antiferromagnetism in (TMTTF)2Br

“…1 The compound (TMTSF) 2 PF 6 is the first organic superconductor, with superconductivity emerging at T c 1.2 K and at pressures above 0.6 GPa, 2,3 with the incommensurate SDW occurring below 13 K at ambient pressure. [4][5][6][7] In (TMTSF) 2 ClO 4 , the superconductivity emerges at 1.2 K at ambient pressure. 8 Determination of charge order is also needed to understand the electronic properties of the (TMTCF) 2 X system.…”