Anisotropy of critical fields of columnar vanadium films

Anisotropy of critical magnetic fields in columnar V films is studied. The position of the additional peak in the Hsub(c)(THETA) curves changes depending on film preparation conditions. It is found that the anomalous behaviour of Hsub(c)(THETA) can be determined both by structural and impurity factors. The effect is discussed in the framework of a model where impurity concentration in the superconductor is periodically modulated by the columnar structure of the samples