Dimensionality crossover induced by a magnetic field in thin metallic films

The field dependence of the magnetoconductance in finite-geometry samples is analyzed within the framework of the localization theory. It is found that for high magnetic fields the magnetoconductance acquires the functional field dependence characteristic of a three-dimensional system. This is so even when the inelastic mean free path is much larger than the sample thickness and when the zero-field transport properties of the system are two dimensional in character. The crossover point is obtained once the radius of the Landau level becomes smaller than the sample thickness for both the parallel and the perpendicular field orientations. These theoretical considerations are borne out by experiments on indium oxide films.