Critical currents in columnar vanadium films

The angular dependence of the critical current Ic is studied in columnar vanadium films. In measurements in constant magnetic fields an anomalous maximum Ic is found on the Ic(θ) curves at arbitrary values of the external magnetic field and temperature, when the magnetic field is perpendicular to the plane of the specimen. The angular dependence of Ic measured in constant reduced magnetic fields h = H/Hc2(T, θ) shows no singularities in the vicinity of the angle at which the Ic peak is found in the case H = const, i.e., the critical current is isotropic. This implies that a change in the relative orientation of the vortices and column boundaries produces no change in critical current. The experimental data obtained permit the conclusion that the anisotropy of Ic observed in a constant magnetic field H is merely a consequence of the anisotropy of the critical magnetic field Hc—the critical current “tracks” the magnitude and angular dependence of Hc.

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