Upper Critical Field, Hall Effect and Magnetoresistance in the Iron-based Layered Superconductor Lafeaso 0.9 F 0.1−δ

By using a two-step method, we successfully synthesized the iron based new superconductor LaFeAsO0.9F0.1−δ. The resistive transition curves under different magnetic fields were measured, leading to the determination of the upper critical field Hc2(T ) of this new superconductor. The value of Hc2 at zero temperature is estimated to be about 50 Tesla roughly. In addition, the Hall effect and magnetoresistance were measured in wide temperature region. A negative Hall coefficient RH has been found, implying a dominant conduction mainly by electron-like charge carriers in this material. The charge carrier density determined at 100 K is about 9.8×10 cm, which is close to the cuprate superconductors. It is further found that the magnetoresistance does not follow Kohler’s law. Meanwhile, the different temperature dependence behaviors of resistivity, Hall coefficient, and magnetoresistance have anomalous properties at about 230 K, which may be induced by some exotic scattering mechanism.