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We report IR and Raman spectra for a two-dimensional superconductor, β′′-(BEDT-TTF)4[Ga(C2O4)3(H3O)]C6H5NO2, below the superconducting transition temperature. The behavior of the lattice-sensitive ...

Low temperature thermodynamic properties of an organic superconductor κ-[(BEDT-TTF)0.95(BEDSe-TTF)0.05]2Cu[N(CN)2]Br where 5% of donor molecules of κ-(BEDT-TTF)2Cu[N(CN)2]Br are substituted by BEDS...

We report the glass-like thermal conductivity behavior of two charge-glass (CG) formers in θ-type organic semiconductors composed by bis(ethylenedithio)tetrathiafulvalene (abbreviated as BEDT-TTF) ...

Angle-resolved heat capacity (ARHC) measurements with multi-directional magnetic fields for an organic superconductor λ-(BETS)2GaCl4 are performed to investigate the out-of-plane (polar angle) and ...

Resistance measurements have been performed to investigate the dimensionality and the in-plane anisotropy of the upper critical field (Hc2) for β-(BDA-TTP)2SbF6 in fields H up to 15 T and at temperatures T from 1.5 to 7.5 K, where BDA-TTP stands for 2,5-bis(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene. The upper critical fields parallel and perpendicular to the conduction layer are determined and dimensional crossover from anisotropic three-dimensional behavior to two-dimensional behavior is found at around 6 K. When the direction of H is varied within the conducting layer at 6.0 K, Hc2 shows twofold symmetry: Hc2 along the minimum Fermi wave vector (maximum Fermi velocity) is larger than that along the maximum Fermi wave vector (minimum Fermi velocity). The normal-state magnetoresistance has twofold symmetry similar to Hc2 and shows a maximum when the magnetic field is nearly parallel to the maximum Fermi wave vector. This tendency is consistent with the Fermi surface anisotropy. At 3.5 K, we found ...

Successive metal–insulator transitions in (DIMET) 2 BF 4 were studied by chopped-light ac calorimetry and electron paramagnetic resonance (EPR) measurement. An anomaly due to the metal–insulator transitions has been clearly detected in ac calorimetry between 20 and 35 K. In contrast to other double-column salts (DMET) 2 BF 4 and (DMET) 2 ClO 4 , successive metal–insulator transitions detected in transport properties are shown to be thermodynamic phase transitions. The EPR detected an anomaly only for the lowest transition around 12 K. The properties of the metal–insulator transitions are compared among the DIMET and DMET salts having the double-column structure. A frequency-dependent step in heat capacity was detected around 110 K. The step-like anomaly is attributed to a glass transition due to freezing of the intramolecular motion of the ethylene group in the ET moiety within a DIMET molecule.

Temperature dependence of the heat capacities of two organic conductors, (DMET) 2 BF 4 and (DMET) 2 ClO 4 , was measured by chopped-light ac calorimetry between 10 and 300 K. A “Mott-like” nature o...

Low-temperature heat capacity of the organic superconductor λ-(BETS)2GaCl4 in a temperature range between 0.6 and 10 K was measured for a single crystal sample by relaxation calorimetry technique. The contribution of electronic heat capacity in the superconducting state shows T2 dependence at lower temperature that indicates the existence of quasi-particle excitations from the line-nodal gap structure of d-wave pairing. The recovery of the electronic heat capacity coefficient, γ by magnetic field shows H1/2 dependence that is consistent with the picture of line-nodal superconductor. In spite of the different packing from typical organic superconductors κ-(BEDT-TTF)2X, the λ-type BETS salt also shows a feature of d-wave symmetry pairing.

Systematic measurements of the magnetic torque of organic π–d conductors κ-(BDH-TTP)2FeX4 (X = Br, Cl) have been performed to investigate the magnetic properties. The Fe 3d spins of both salts show antiferromagnetic (AF) orders at low temperatures. A simple two-sublattice model is found to well reproduce the essential features of the torque data in the AF states. The exchange interaction and anisotropic parameter of the ligand field obtained by the simulations are consistent with previous experimental results.

Resistance, magnetic susceptibility, magnetic torque, and ESR measurements have been performed to investigate the electronic state of the two-dimensional organic conductor κ-(BDH-TTP)2FeCl4. The temperature dependence of the resistance shows monotonic metallic behavior down to 30 mK, and the magnetic susceptibility, arising mainly from the Fe \(3d\) spins, follows the Curie–Weiss law down to 2 K. At low temperatures below 0.4 K, the magnetic torque steeply changes at low magnetic fields, associated with a sign change. The systematic measurements elucidate that the \(3d\) spins undergo an antiferromagnetic order at about 0.4 K and that the torque sign change is caused by a spin-flop transition. A rapid decrease of the magnetoresistance at the spin-flop field provides clear evidence of a finite π–\(d\) interaction. Characteristic temperature dependences of the magnetic susceptibility and ESR \(g\)-value are found in the paramagnetic phase, which are explained in terms of the single-ion anisotropy effect.

The structure and physical properties of metallic magnetic conductor κ-(BDH-TTP)2FeBr4 (BDH-TTP: 2,5-bis(1,3-dithiolan-2-ylidene)-1,3,4,6-tetrathiapentalene) are investigated. It has a layered structure of BDH-TTP donor sheets extended along the \(ac\)-plane, which are sandwiched by FeBr4 anion sheets. The π electrons on the BDH-TTP sheets show simple metallic behavior down to 30 mK. The magnetic susceptibility obeys the Curie–Weiss law mainly associated with the Fe3+ \(d\) spins (\(S = 5/2\)), and indicates the presence of an anitiferromagnetic (AF) transition at \(T_{\text{N}} = 3.9\) K. In the AF state, a steep S-shaped increase of the magnetization at 1.5 T (\(H_{\text{SF}}\)) in the field parallel to the \(a\)-axis (\(H\parallel a\)) is found, which is ascribed to a spin-flop transition. In addition, the magnetization curves for \(H\parallel b\) and \(H\parallel c\) show an inflection point at \(H_{\text{c}} = 3.1\) T, suggesting the spin canting configuration in the \(bc\)-plane. A possible AF spin ...