Physical Properties of a new Low-dimensional Conductor HfTes

过渡金属五碲化物ZrTe_5和HfTe_5在低维导体领域引起了人们的兴趣。首次在HfTe_5中发现了70 K附近的一个强电阻率峰，为合成无杂质HfTe_5单晶提供了线索。本研究计划的目的是通过各种实验尽可能地研究其丰富的物理性质，并澄清HfTe_5中电阻率峰的起源。[1982-1983]针对电阻率峰的起源，对磁电阻、霍尔系数和42 T脉冲磁场下的电阻进行了大量的测量，并对峰温以下的磁化强度进行了研究。根据观察到的Shubnikov-de哈斯振荡确定了HfTe_5和ZrTe_5的长香烟形椭球费米面。利用得到的输运参数半定量地解释了各向异性电导率。[1984-1986]另一方面，我们用四圆X射线衍射仪对低至7 K的单晶X射线衍射进行了深入的研究。特别是对HfTe_5在17 K下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。在本研究中，在17 K和室温之间没有观察到HfTe_5的明显晶格位移。

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.