Upper critical field, Hall effect and magnetoresistance in the iron-based layered superconductor LaFeAsO0.9F0.1−δ

By using a two-step method, we successfully synthesized the new iron-based superconductor LaFeAsO 0.9 F 0.1−δ . The resistive transition curves under different magnetic fields were measured, leading to the determination of the upper critical field H c2 ( T ) of this new superconductor. The value of H c2 at zero temperature is estimated to be about 50 T roughly. In addition, the Hall effect and magnetoresistance were measured in a wide temperature region. A negative Hall coefficient R H 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 20 cm −3 , which is close to the cuprate superconductors. It is further found that the magnetoresistance does not follow Kohler's law. Meanwhile, the different temperature-dependent behaviors of resistivity, Hall coefficient and magnetoresistance have anomalous properties at about 230 K, which may be induced by some exotic scattering mechanism.