Single crystal growth of iron oxypnictides and physical properties under high pressure

成功制备了新铁氧nictide Sr2Cr2Fe2As2O2。在铁-砷四面体之间具有层状结构的铁氧nictides中，如Sr2Cr2Fe2As2O2，预计会有更高的超导转变温度。然而，元素替代掺杂和施加13 GPa的压力都不会导致Sr2Cr2Fe2As2O2的超导性。Sr2Cr2Fe2As2O2体系中超导性的抑制可能与Cr原子的磁序有关。我们尝试用钨金属坩埚制备Sr2Cr2Fe2As2O2单晶样品。然而，电炉中气体的纯度不足以防止金属坩埚熔化。因此，我们无法生长出Sr2Cr2Fe2As2O2的单晶样品。Sr2Cr2Fe2As2O2和某些单质取代化合物都很弱，因此在高压下合成适合于这种材料。建立了高压下霍尔电导率的测量系统。

New iron oxypnictide Sr2Cr2Fe2As2O2 successfully prepared. Higher superconducting transition temperature is expected in iron oxypnictides with the layered structures between Fe-As tetrahedrons, like Sr2Cr2Fe2As2O2. However, neither elemental substitution for doping careers nor applying pressure of 13 GPa, does cause the superconductivity in Sr2Cr2Fe2As2O2. Suppression of the superconductivity in Sr2Cr2Fe2As2O2 system is probably due to magnetic order of Cr atom. We tried to prepare single crystal samples of Sr2Cr2Fe2As2O2 with metal crucibles with tungsten metal. However, purity of gas in the electrical furnace was not enough to prevent the metal crucibles from melting. As a result, we could not grow the single crystal sample of Sr2Cr2Fe2As2O2. Sr2Cr2Fe2As2O2 and some kinds of elemental substituted compounds are very weak, so that synthesizing under high pressure is suitable for this material. Measurement system for Hall conductivity under high pressure was established.