R. Inada

Hall effect of 1T-TaS2

Abstract The Hall coefficient of a 1T-TaS 2 single crystal was measured from 360 K to 1.4 K. An abrupt change of the sign and a hysteresis were observed in the Hall coefficient at the nearly commensurate-commensurate phase transition temperature, ca. 200 K; above this temperature the major carrier was n-type, and below, p-type.

Anomalous magnetoresistance in 1T-TaS2

Abstract Transverse magnetoresistance of 1T-TaS 2 was measured in magnetic fields up to 100 kOe in the semiconductive region corresponding to the commensurate charge density wave (CDW) state.

Electrochemical characteristics of transition-metal trichalcogenides in the secondary lithium battery

Abstract Transition-metal trichalcogenides have been investigated as cathode materials in the lithium electrochemical cell. Three lithium ions per TiS3 molecule have been found to be marginally reversible, while only one lithium is reversible in TaSe3. This difference may be related to exfoliation of these substances due to the progress of lithium intercalation.

Electrochemical Characteristics of TiS2, ZrSe2 and VSe2 in Secondary Lithium Battery

The layered transition metal dichalcogenides of TiS2, ZrSe2 and VSe2 were found to react reversibly with lithium in electrochemical cells. The energy densities of these cathode materials were determined to be 500, 240 and 250 Wh/kg for one lithium intercalation per unit cell, respectively and 420 Wh/kg for two lithium intercalation per unit cell of VSe2. It was found for ZrSe2 that more than two lithium ions per unit cell can be intercalated in the first discharge when the cell temperature is increased to 60°C, while one lithium ion can be intercalated at 20°C.

Hall effect of 1T-TaS2 and 1T-TaSe2

Abstract The Hall coefficients of 1T-TaS2 and 1T-TaSe2 single crystals were measured from 360 K to 1.4 K. An abrupt change of the sign and a hysteresis were observed in the Hall coefficient of 1T-TaS2 at the nearly commensurate-commensurate phase transition temperature, ca. 200 K; above this temperature the major carrier was n-type, and below, p-type. On the other hand, the sign of Hall coefficient of 1T-TaSe2 was positive in the whole temperature range measured.

Superconductivity of alkali metal intercalated ZrSe2

Abstract Alkali metal intercalated ZrSe 2 (A x ZrSe 2 ) has been synthesized by the reaction of ZrSe 2 single crystals with n-butyllithium in hexane solution, or alkali metal (Na, K, Rb, Cs) in hexamethylphosphoric triamide solution. Semiconductive ZrSe 2 has been converted into a metallic substance by the alkali metal intercalation. Superconductivity has been found for Li x -, Na x -, K x , Rb x and Cs x ZrSe 2 (0 x ⩽ 1) below 1.7, 2.0, 2.1, 1.7, and 1.4, respectively. The angular dependence of the upper critical fields H c2 for A x ZrSe 2 is interpreted by the effective mass model. The Ginzburg-Landau coherence lengths perpendicular to the layer planes of the crystals at zero temperature are ten to twenty times larger than the layer repeat distances, showing a three dimensional character. Anisotropic superconductivity is discussed on the basis of the Fermi surface of A x ZrSe 2 whose electron number is determined by the charge transfer from alkali metal atoms to ZrSe 2 .

Effect of impurities of selenium and iron on the Anderson localization of 1T-TaS2

Abstract The temperature dependence of electrical resistivities θ( T ) of 1T-TaS 2 , 1T-TaS 2- x Se x and 1T-Fe x Ta 1- x S 2 is found to be θ( T ) ∝ exp( T 0 / T ) 1/n in the temperature range of 4 K to the measured lowest temperature, 0.1 K, showing the variable range hopping of Anderson localized states. The n -value is nearly 3 for selenium doping and nearly 2 for non-doping and iron doping. The positive magnetoresistance, which is sizable only in the temperature range of 2 K to 0.5 K in 1T-TaS 2 , is found to be remarkably enhanced by the selenium doping, while the tendency is reversed by the iron doping.

Anomalous phonon scattering responsible for the electron relaxation time in the longitudinal magneto-resistance in bismuth

Anomalous longitudinal Shubnikov-de Haas oscillation of bismuth which was found by the authors is confirmed by extending the experimental temperature range up to 40K. With the temperature rise, the oscillation amplitude increases remarkably at lower temperatures, saturates and decreases slowly at higher temperature. The effect is explained by considering two types of relaxation mechanisms of electron orbits, i.e., intra-Landau level and inter-Landau level scatterings due to phonons. Phonons responsible for the inter-level scatterings are less excited at lower temperature and give the observed anomalous effect. A numerical estimate has been presented.

Structural Phase Transition in Stage 2 SbCl5-Graphite Intercalation Compound

The structural phase transition of stage 2 SbCl 5 -graphite intercalation compound made from a single crystal of Kish graphite has been investigated by the electron diffraction, specific heat and static susceptibility below 300 K. The phase transition can be explained by the presence of two kinds of species for antimony chlorides. One of these species undergoes a commensurate-incommensurate phase transition at T cu (=230 K) of first order, and above T cu it forms a discommensuration structure in which the (\(\sqrt{7} \times \sqrt{7}\))R19.11° superlattice is modulated by the honeycomb domain structure. The other species remains unchanged as the (\(\sqrt{7} \times \sqrt{7}\))R19.11° structure at least above T c1 (=210 K). Below T c1 , there appears the glassy phase which is identified as the (\(\sqrt{7} \times \sqrt{7}\)) structure without directional long range order.

Electrochemical characteristics of ZrSe2 in a secondary lithium battery

Abstract Electrochemical characteristics of the transition metal dichalcogenide ZrSe2 were investigated as a cathode material. Lithium intercalated ZrSe2 showed a high reversibility of lithium ions in the non-aqueous solution. The discharge/ charge cycle was performed up to 160 times without deterioration.