Experimental studies on the weakly ferromagnetic metals and the quasi-one-dimensional organic charge transfer salts

Weakly magnetic metals and quasi-1D organic charge transfer salts are two examples of strongly correlated electron systems, and the phase transitions of both can be tuned by application of hydrostatic pressure. Here we examine several weakly ferromagnetic metals and quasi-ID organic charge transfer salts using high pressure NMR, transport, and susceptibility.; The zero-field NMR of high-pressure MnSi reveals an inhomogeneous magnetic phase starting from an intermediate pressure P*, and local magnetism surviving far beyond the critical pressure PC. This phase inhomogeneity may lead to the non-Fermi liquid behavior in the high-pressure paramagnetic phase. However, the origin of phase inhomogeneity, whether due to slow fluctuations on the border of a first order phase transition, or due to spin-orbit coupling, is still unclear. Susceptibility studies on rhodium-doped MnSi demonstrate strong coupling between disorder and antiferromagnetic correlations by the formation of a spin glass state. The implications for the high pressure MnSi, where the fluctuations are expected to be more prominent, deserve further study.; Our NMR and transport studies on the quasi-1D organic charge transfer salts (TMTCF)2X, indicate that charge ordering is stabilized through the combination of coupling to anionic motion, and long range intrastack Coulomb interactions. The charge ordering is found to suppress the spin-Peierls state and cooperate with antiferromagnetism. Based on this, we have established a new phase diagram for this class of materials. We looked for evidence of charge fluctuations in the metallic phase. Evidence for their existence is established by NMR spectroscopy.; The nature of the low temperature conducting phase remains undetermined. Experiments give evidence for both Fermi liquid and non-Fermi liquid properties.