Physical Properties of a new Low-dimensional Conductor HfTes

过渡金属五碲化合物ZrTe_5和HfTe_5在低维导体领域引起了人们的兴趣。我们首次在HfTe_5中发现了70K附近的强电阻峰，为合成无杂质HfTe_5单晶提供了线索。本研究项目的目的是通过各种实验尽可能研究其丰硕的物理性质，并阐明HfTe_5中电阻峰的来源。[1982-1983]关于峰的来源，我们在高达42T的脉冲磁场下进行了磁阻、霍尔系数和电阻的测量，并结合低于该峰温度的磁化作用进行了研究。结果由观测到的Shubnikov-de Haas振荡确定了HfTe_5和ZrTe_5的长烟形椭球费米面。另一方面，我们利用四圆X射线衍射仪对7K以下的单晶X射线衍射进行了深入的研究。特别是对HfTe_5在17K时的晶体结构进行了测定，并与室温下的晶体结构进行了比较。在本文的X射线研究中，在17K-室温范围内没有观察到HfTe_5明显的晶格位移。

The transition-metal pentatellurides ZrTe_5 and HfTe_5 have been attracting the interest in the field of low-dimensional conductors. We found out a strong electrical resistivity peak around 70 K in HfTe_5 for the first time and we also obtained a clue to synthesize single crystals of impurity-free HfTe_5. The purpose of this research project is to study its fruitful physical properties as far as possible by various experiments and to clarify the origin of the resistivity peak in HfTe_5.[1982-1983] with respect to the origin of the resistivity peak, the measurements of magnetoresistance, Hall coefficient and resistance under the pulsed magnetic field up to 42 T have been intensively done together with magnetization study below the temperature of the resistivity peak. As the result the long cigarette shaped ellipsoidal Fermi surfaces of HfTe_5 and ZrTe_5 were determined by the observed Shubnikov-de Haas oscillation. The anisotropic conductivity was explained semi-quantitatively by using the obtained transport parameters.[1984-1986] On the other hand we have performed the intensive study of single crystal X-ray diffraction down to 7 K by using four-circle X-ray diffractometer. Especially, the determination of the crystal structure of HfTe_5 at 17 K was carried out and its result was compared with the crystal structure at room temperature. In the present X-ray study, no remarkable lattice displacement was observed in HfTe_5 between 17 K and room temperature.