Muon spin relaxation studies in organic superconductors and organic magnets

Muon spin relaxation (μSR) measurements of the magnetic field penetration depth λ in (BEDT-TTF)2-X, alkali-doped fullerenes, and (TMTSF)2ClO4 have shown that these organic superconductors are characterized by large ratios of Tc/TF = 0.01 ∼ 0.1, where TF represents an effective Fermi energy for the low-energy response of the superconducting carriers. Zero-field μSR studies of the spin density waves (SDW) in (TMTSF)2-X revealed a very sharp change of the order parameter near TN with a common SDW amplitude for X = PF6, NO3 and ClO4. We also present the temperature dependence of the spontaneous magnetic field in an organic ferromagnet β phase p-NPNN.