论文标题
ndfeas(O,F)薄膜的转运性能的各向异性
Anisotropy of the transport properties of NdFeAs(O,F) thin films grown on vicinal substrates
论文作者
论文摘要
ndfeas(O,f)具有不同氟含量的薄膜在5度上生长。或10度。通过分子束外延状的近代切割MGO和CAF2单晶底物。通过反射高能电子衍射和X射线衍射的结构特征证实了NDFEAS的外延生长(O,F)。 AB平面的电阻率和沿C轴的电阻率是从纵向和横向方向的电阻率测量得出的。 C轴电阻率总是高于AB平面电阻率,这是由于各向异性电子结构所致。在300 K处的电阻率各向异性在50-90的范围内几乎是恒定的,无论F含量如何。另一方面,在56 K处的电阻率各向异性表现出很强的氟依赖性:对于具有最佳F含量的薄膜(超导性过渡温度TC左右)的电阻率各向异性超过200,而在未掌管的35和45 k之间的膜中的电阻率各向异性均为70。 The mass anisotropy are the effective masses along the c-axis and on the ab-plane) close to Tc derived from the anisotropic Ginzburg-Landau approach using the angular-dependency of the ab-plane resistivity was in the range from 2 to 5. On the assumption that the square of the mass anisotropy is equal to the resistivity anisotropy, those values are small compared to the normal state anisotropy.
NdFeAs(O,F) thin films having different fluorine contents were grown on 5 deg. or 10 deg. vicinal cut MgO and CaF2 single crystalline substrates by molecular beam epitaxy. Structural characterisations by reflection high-energy electron diffraction and x-ray diffraction confirmed the epitaxial growth of NdFeAs(O,F). The resistivities of the ab-plane and along the c-axis were derived from the resistivity measurements in the longitudinal and transversal directions. The c-axis resistivity was always higher than the ab-plane resistivity, resulting from the anisotropic electronic structure. The resistivity anisotropy at 300 K was almost constant in the range of 50-90 irrespective of the F content. On the other hand, the resistivity anisotropy at 56 K showed a strong fluorine dependence: the resistivity anisotropy was over 200 for the films with optimum F contents (superconducting transition temperature Tc around 50 K), whereas the resistivity anisotropy was around 70 for the films in the under-doped regime (Tc between 35 and 45 K). The mass anisotropy are the effective masses along the c-axis and on the ab-plane) close to Tc derived from the anisotropic Ginzburg-Landau approach using the angular-dependency of the ab-plane resistivity was in the range from 2 to 5. On the assumption that the square of the mass anisotropy is equal to the resistivity anisotropy, those values are small compared to the normal state anisotropy.