Zero-Field Muon Spin Rotation Studies in (TMTSF)2PF6

We report zero-field muon spin rotation studies of the organic compound (TMTSF)2PF6 at ambient pressure. An extremely sharp onset of the spin density wave state (SDW) is observed below the transition temperature TM = 12.2 K, which may be first order in nature. The saturation of the magnetic order at low temperatures can be ascribed to the existence of the SDW gap. The broad distribution of local magnetic fields deduced from μSR time spectra is consistent with that expected from an incommensurate SDW.