Anisotropy of flux flow in layered superconductor 2H-NbSe2−x S x

Magnetic-field dependence of the resistivity for various currents in the layered superconductor 2H-NbSe_1.8S_0.2 was investigated. The flux flow was observed for various angles between the magnetic-field direction and the crystal layers near zero-field critical temperature. Anisotropy of the pinning force and the viscosity coefficient was found. The peak effect was observed under a magnetic field perpendicular to the layers, while it was not observed under a magnetic field parallel to the layers. A strong pinning force was found acting only on flux lines parallel to the layers. These results can be explained by the pinning mechanism due to the stacking faults.