Size effects under a strong magnetic field : transverse magnetoresistance of thin gold films deposited on mica

We report measurements of transverse magnetoresistance where the signal can be attributed to electron–surface scattering, together with measurements of the surface roughness of the films on an atomic scale. The measurements were performed with a scanning tunnelling microscope (STM) on four thin gold films evaporated onto mica. The magnetoresistance exhibits a marked thickness dependence: at 4 K and 9 T is about 5% for the thinner (69 nm) film, and about 14% for the thicker (185 nm) film. Sondheimer's theory provides an accurate description of the temperature dependence of the resistivity, but predicts a magnetoresistance one order of magnitude smaller than that observed at 4 K. Calecki's theory in the limit of small roughness correlation length, predicts a resistivity two orders of magnitude larger than observed at 4 K.