Transport properties and the large anisotropic magnetoresistance of CuxNbS2 single crystals
The transport properties of CuxNbS2 (x = 0.09, 0.44 and 0.55) single crystals were systematically studied. The in-plane and out-of-plane resistivities decrease with increasing Cu content, and a transition with hysteresis shows up for the crystals with x = 0.44 and 0.55. The thermopower and Hall coefficient of CuxNbS2 show opposite signs, indicating that there are two kinds of carriers in this system. The angular dependences of the in-plane magnetoresistance (MRab = (ρab(H)−ρab(0))/ρab(0) × 100%) at different temperatures were also studied. The single crystals with x = 0.44 and 0.55 show a strong anisotropic MRab. For the x = 0.55 sample, MRab reaches 80% with a magnetic field of 14 T applied along the c-axis, while MRab is less than 5% for the magnetic field applied within the ab-plane. These results can be well understood in the light of the anisotropic Fermi surface in the multiband system.
Electron diffraction investigation of the AgxTaS2 system. I. Superlattices in Ag1/8TaS2 and Ag2/3TaS2
Superlattices are observed by electron diffraction in electrolytically prepared single crystals of stage 1 Ag2/3TaS2 and stage 2 Ag1/3TaS2 intercalation compounds in the temperature region from 300 to 25 K. These superlattice satellites are explained as ordered silver ion superstructures. The silver ions in both compounds undergo an order-disorder transition in two stages. The first occurs near room temperature and leaves about 25% of the silver ions disordered, which in turn order in the second transition near 90 K. 
 
 
 
Uberstrukturen werden mit Hilfe der Elektronenbeugung in elektrolytisch hergestellten Einkristallen von AgxTaS2 Einlagerungsverbindungen erster Stufe (x = 2/3) und zweiter Stufe (x = 1/3) im Temperaturbereich von 300 bis 25 K beobachtet. Diese Uberstruktursatelliten konnen als geord-nete uberstrukturen der Silberionen erklart werden. Die Silberionen in beiden Verbindungen durchlaufen Ordnungs-Unordnungs-ubergange in zwei Stufen. Der erste kommt bei Raumtem-peratur vor und last ungefahr 25% der Silberionen ungeordnet, die sich dann bei einem zweiten ubergang bei 90 K ordnen.
The non-stoichiometric phases Nb1+xSe2 and Ta1+xSe2
The non-stoichiometric phases M1+xSe2 (M = Nb, Ta; 0 < x < 0.3) have structures built from MSe2 slabs with M in trigonal-prismatic coordination; the x additional metal atoms lie in octahedral holes between the slabs. Depending on the composition and the temperature of preparation, various forms of M1+xSe2 are obtained which differ in the stacking of the MSe2 slabs. Samples prepared at 800 °C, for instance, are of the 3s- and 2s(b)-forms for 0.05 ⩽ x ⩽ O.15, while more metal-rich samples are of the 2s(a)-form. The metal-rich limit of the homogeneity range at 800 °C lies at about x = 0.29 for Nb1+xSe2, and at about x = 0.21 for Ta1+xSe2. The phases M1+xSe2 are metallic with nearly temperature-independent paramagnetism.