Structure and Physical Properties of EDT-TTF Salts
- PDF / 997,596 Bytes
- 6 Pages / 414.72 x 648 pts Page_size
- 74 Downloads / 218 Views
ABSTRACT Charge-transfer salts of EDT-TTF with tetrahedral anions MX 4 (M -Fe, Ga ; X Cl, Br) were prepared. They are isostructural to each other (monoclinic P2 1/m) with the stoichiometry of 2:1. All of them are semiconductors having the conductivity at room temperature of 5 to 9 Scm-1 and activation energy of 40 to 170 meV. Since the calculated band structure of them indicate that they should be quasi one-dimensional metals, they were discussed from the point of structural deformation and strong electron correlation. INTRODUCTION EDT-TTF(ethylenedithio-tetrathiafulvalene) is one of the most typical hybrid TTF-based donor molecule between BEDT-TTF and TTF(Fig. 1)[1]. The studies on the EDT-TTF salts were reported for octahedral, tetrahedral and linear anions [2,3] and intensive examinations were performed for superconducting ot-(EDT-TTF)(Ni(dmit)j] [4,5,6], in which both the donor (EDT-TTF) and anion columns ([Ni(dmitQj) construct the metallic (superconducting) Fermi surfaces. Because of the poor ability of EDT-TTF to yield the stable metallic or superconducting salt in comparison with BEDT-TTF, an intensive study on the EDT-TTF complexes has not been
perfonned except for the reported papers listed above. An elimination of one ethylenedithio moiety from a BEDT-TTF induces a relatively large on-site coulomb repulsion for EDT-TTF. With respect to this, it is of interest to develop new conducting materials having strong electronic correlation. Furthermore, the magnetic exchange interactions between the conducting n-electrons on the donor molecules and localized magnetic moments on the anions is also of interest if they exist. With these scopes, we synthesized new charge-transfer salts of EDT-TTF, mainly for anions with tetrahedral structure, solved the crystal structures, and measured transport and magnetic properties. S S> -< SS: r1 S> _ S S)
CS
S EDT-TTF
Figure I
S
S
BEDT-TTF
Chemical structure of EDT-TTF and BEDT-TTF
EXPERIMENT Preparation of single crystals was performed by the galvanostatic electro-crystallization 921 Mat. Res. Soc. Symp. Proc. Vol. 488 ©1998 Materials Research Society
method with a current of 0.5[.A. The intensity data of the structural analysis were collected on MAC SCIENCE MXCX four circle diffractometer. X-ray oscillation photographs were taken on MAC SCIENCE DIP-2000K Imaging Plate System at room temperature and 105K using Oxford low temperature cryostat MOCS-2. The d.c. conductivities were measured based on a standard four-probe method. Measurements of the magnetization were performed by the aid of Quantum Design MPMS-2 and MPMS-5S magnetometers in the temperature range of 2.0 to 300K and magnetic field of 100Gauss. RESULTS AND DISCUSSION Single crystals of good quality were obtained for the tetrahedral anions (FeX 4 and GaX 4 ; X=Cl, Br) which enable us both the single crystal structure determination and measurement of the transport and magnetic properties with good accuracy. Crystals with clear edges were also obtained for linear (13) and polymeric type anions (Cu(NCS) 2), tho
Data Loading...
