Anisotropic fluctuation conductivity of thin superconducting films of transition metals

The angular dependence of the width of superconducting transitions in a magnetic field in thin vanadium and niobium films in the region of strong fluctuations is studied. Two special orientations of the magneic field relative to the surface of the film were discovered: the angle θ0 at which the width of the transition is maximum and the angle θt separating the region of angles in one of which the fluctuation behavior is determined solely by the component of the external magnetic field perpendicular to the film, while in the other the magnitude of the parallel component is also significant. The dependence of θ0 and θt on the temperature is studied. The experimental data are in qualitative agreement with the theory describing the orientational dependence of the smearing of the transitions for two-dimensional superconductors in the region of weak fluctuations. The three-dimensional phase diagaram in the space H, T, and θ, determining the critical region, is constructed.

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