The measurement of electron mean free paths in potassium using the radio-frequency size effect

Radio-frequency size effect measurements have been made on parallel plate polycrystal and single-crystal samples of potassium in the temperature range 1.9-4.2 degrees K and at frequencies from 1 to 4 MHz. The r.f. size effect signal which arises from electrons near the elliptic limiting point on the Fermi surface was observed by sweeping the tip angle between the magnetic field H and the sample surface, at a fixed value of H. The variation in amplitude of these signals with H was used to infer an electronic mean free path at a fixed temperature, and also to study its temperature dependence.