Toshikazu Nakamura

Possible charge ordering patterns of the paramagnetic insulating states in (TMTTF)2X

ESR investigations were performed for a series of quasi-one-dimensional organic conductors, (TMTTF) 2 X . The ESR linewidth shows abrupt jumps or humps in the paramagnetic insulating region. The (TMTTF) 2 X salts are roughly divided into three groups according to the anisotropy of the ESR linewidth at low temperatures. In this paper, we discuss the possible charge-ordered patterns of three typical salts ( X =ReO 4 , SbF 6 and Br) from the microscopic point of view.

Charge ordering in θ-(BEDT-TTF)2RbZn(SCN)4

The electronic state of θ-(BEDT-TTF) 2 RbZn(SCN)4 has been investigated by the precise analyses of the angular dependence of 13 C-NMR lineshape. It is found that the metal-insulator transition observed at 190 K at ambient pressure is of a novel type accompanied with a charge re-distribution in the organic layer. In the insulating state, the electric charges order as a stripe along the a-axes and the charge rich and poor sites alternate along the c-axes. The spin-singlet phase below 30 K is recognized as a spin-Peielrs transition of the 1D spin system.

Magnetic Investigation of Possible Quasi-One-Dimensional Two-Leg Ladder Systems, (BDTFP)2X(PhCl)0.5 (X = PF6, AsF6)

ESR and 1 H-NMR investigations of the quasi-one-dimensional organic conductors, (BDTFP) 2 X (PhCl) 0.5 ( X = PF 6 , AsF 6 ), were carried out. The low-temperature physical properties of the title c...

NMR study of charge localized states of (TMTTF)2Br

Abstract 13C NMR study was performed for a quasi-one-dimensional organic conductor (TMTTF)2Br, using a single crystal in which two central carbon sites of TMTTF molecules were labeled with 13C. To investigate the relation between the charge localization around 100xa0K and the magnetic ground state from the microscopic point of view, we measured the NMR spectra and nuclear relaxation rate. We found slight broadening of the spectra above the magnetic phase transition temperature (T N ∼15 K ). We discuss this anomaly with the newly measured data of uniform susceptibility and ESR.

NMR investigation of (TMTTF)2Br: charge configurations and spin dynamics

Abstract We performed 13 C NMR study for a quasi-one-dimensional organic conductor (TMTTF) 2 Br. Although the resistivity has its minimum value around 100xa0K, the NMR spectra showed no significant change down to 30xa0K. Instead, we found slight broadening of the spectra above the magnetic phase transition temperature ( T N ∼15xa0K). Similar anomaly is also observed for the uniform susceptibility ( χ s ).

Low-temperature electronic phases of EDT-TTF based molecular conductors

Magnetic investigation was carried out for low temperatures electronic phases in (EDT-TTF) 2 AuBr 2 , which undergoes an SDW transition at 16 k. In the SDW phase, we observed an abrupt change of 1 H-NMR absorption line around 6 K where the 1 H-NMR spin-lattice relaxation rate shows an anomalous second peak. The electronic phase is discussed by microscopic point of view.

Microscopic Investigation of a New Two-Component Organic Conductor with Itinerant and Localized Spins: (CHTM-TTP)2TCNQ

Low-temperature electronic phases in a new two-component organic conductor, a segregated-stack charge-transfer salt called (CHTM-TTP) 2 TCNQ, are investigated. The ESR g tensor analyses indicate th...

ESR Investigation of Charge Localized States in (TMTTF)2X

ESR investigations were performed for a series of organic conductors, (TMTTF) 2 X (X=SbF 6 , AsF 6 , PF 6 , ReO 4 , ClO 4 , SCN, Br). The ESR linewidth shows abrupt jumps or humps in the paramagnetic insulating region. The (TMTTF) 2 X compounds are roughly divided into three groups in the aspect of the anisotropy of the ESR linewidth at low-temperatures. We discuss the low-temperature charge distributed pattern from the microscopic point of view.

ESR study of the charge ordering in (TMTTF)2X

Abstract ESR studies of the quasi-one-dimensional organic conductors, (TMTTF)2ReO4, were carried out. The ESR line width shows an discontinuous drop at 154 K , and its anisotropy also changes. In the low temperature phase, the electronic dipoles contribute to the ESR line width. We discuss the possible charge ordering patterns from the microscopic point of view.

Pressure dependence of the SDW transition in (TMTTF)2Br

We investigated the pressure dependence of the resistivity in (TMTTF) 2 Br, applying with pressure up to 1.2GPa. At ambient pressure the resistance shows the kink structure at 18K where the spin susceptibility starts to decrease, despite the AF transition occurs at 14K. With increasing pressure, the peak of the derivative of the resistance appears 4-8K above the AF transition. Its suggested to be the new phase transition above the AF transition. Above 0.5GPa, the pressure dependence of T SDW is consistent with the prediction of the mean field theory.