Search

The radical anion salt [Fe{HC(pz)3}2](TCNQ)3demonstrates conductivity and spin-crossover (SCO) transition associated with Fe(II) complex cation subsystem. It was synthesized and structurally characterized at temperatures 100, 300, 400, and 450 K. The compound demonstrates unusual for 7,7,8,8,-tetracyanoquinodimethane (TCNQ)-based salts quasi-two-dimensional conductivity. Pronounced changes of the in-plane direct-current resistivity and intensity of the electron paramagnetic resonance (EPR) signal, originated from TCNQ subsystem, precede the SCO transition at the midpoint T* = 445 K. The boltzmannian growth of the total magnetic response and structural changes in the vicinity of T* uniquely show that half [Fe{HC(pz)3}2] cations exist in high-spin state. Robust broadening of the EPR signal triggered by the SCO transition is interpreted in terms of cross relaxation between the TCNQ and Fe(II) spin subsystems.

No Abstract

It is shown, that doping by chlorine atoms changes the type of conductivity of Bi2Te3from p- to n-type as well as the character of conductivity. In the direction perpendicular to the layers plane phonon assisted hopping conductivity is observed. The mechanism of charge transport in Bi2Te3crystals doped by chlorine atoms is proposed.

The transport and superconducting properties of Ba1-xKxFe2As2single crystals were studied. Both in-plane and out-of-plane resistivity were measured by Montgomery method. The in-plain resistivity temperature dependence was found to be nonlinear with the tendency to saturate at high temperature. We have found that the resistivity anisotropy is almost independent of temperature and lies in the range 10--40 for the studied samples. We explain this result by the extrinsic nature of high out-of-plane resistivity, which may be due to the presence of flat defects along Fe--As layers. This statement is supported by comparatively small effective mass anisotropy, obtained from the upper critical field measurements.