Spin-flop switching and memory in a molecular conductor.

We report the first observation of spin-flop-induced sharp positive magnetoresistance as large as 100% and nonvolatile magnetoresistive memory in a π-d hybrid molecular conductor, (DIETSe)(2)FeCl(4) [DIETSe = diiode(ethylenedithio)tetraselenafulvalene]. The unprecedented magnetotransport phenomena originate from the coexistence of the spin density wave (SDW) of the quasi-one-dimensional (Q1D) π electrons and the antiferromagnetic order of d-electron spins, indicating the interplay between the electronic instability of Q1D π electrons and local moments of antiferromagnetic d-electron spins. These findings offer new possibilities in molecular electronics/spintronics.

Ambient-pressure organic superconductors kappa-(DMEDO-TSeF)2[Au(CN)4](solv.): Tc tuning by modification of the solvent of crystallization.

The unsymmetrical pi donor dimethyl(ethylenedioxy)tetraselenafulvalene (DMEDO-TSeF) has provided six new organic superconductors with a monovalent square-planar [Au(CN)(4)](-) ion and cyclic ethers as solvent of crystallization. The six new organic superconductors kappa-(DMEDO-TSeF)(2)[Au(CN)(4)](solv.) [solv.=1,3-dioxolane (DOL), 2,5-dihydrofuran (DHF), tetrahydropyran (THP), 1,3-dioxane (1,3-DOX), 3,4-dihydro-2H-pyran (DHP), or 1,4-dioxane (1,4-DOX)] are classified into two subphases kappa(L) and kappa' according to the differences in their space group symmetry. kappa(L)-(DMEDO-TSeF)(2)[Au(CN)(4)](solv.) (solv.=DOL, DHF, THP, 1,3-DOX or DHP) crystallizes in the orthorhombic space group Pnma, and T(c) of the kappa(L) phase varies by 1.7-5.3 K according to the size and shape of the solvent of crystallization. On the other hand, kappa'-(DMEDO-TSeF)(2)[Au(CN)(4)](solv.) (solv.=DOL or 1,4-DOX) crystallizes in the noncentrosymmetric monoclinic space group Cc. The kappa'-phase containing 1,4-DOX shows superconductivity at 4.2 K, but the kappa'-phase containing DOL does not show superconductivity down to 1.4 K. Systematic investigation of the six new organic superconductors, together with the two previously reported superconductors kappa(H)- and kappa(L)-(DMEDO-TSeF)(2)[Au(CN)(4)](THF), revealed that the T(c) of the present system is finely tunable by utilizing the effect of the solvent of crystallization.

New ambient pressure organic superconductors kappa H- and kappa L-(DMEDO-TSeF)2[Au(CN)4](THF).

We have developed two novel organic superconductors kappa H- and kappa L-(DMEDO-TSeF)2[Au(CN)4](THF) (DMEDO-TSeF = dimethyl(ethylenedioxy)tetraselenafulvalene) with the onset transition temperatures of 4.8 K for the kappa H-phase and 3.0 K for the kappa L-phase at ambient pressure, where DMEDO-TSeF is the second example following tetramethyltetraselenafulvalene (TMTSF) after an interval of 25 years as a sulfur-free donor providing a bulk organic superconductor.

Synthesis, crystal structure and electrochemical properties of bis(ethylenedioxy)tetraselenafulvalene (BEDO-TSeF).

Bis(ethylenedioxy)tetraselenafulvalene (BEDO-TSeF) has been synthesized using elemental selenium as the only source of the selenium atoms, and its crystal structure and electrochemical properties are examined and compared with its sulfur analogues.