Size Dependence of Magnetoresistance of Many‐Valley Semiconductors

The dependence of the magnetoresistance (MR) is studied of a many‐valley semiconductor with thickness 2 d (‐ d ≦ y ≦ d) comparable with the length of the intervalley scattering and/or the cooling length when the correlation between them is arbitrary. If a weak electric current flows along the x‐axis the MR monotonously reduces in a magnetic field H = H_z when the thickness decreases and for d → 0 it becomes equal to zero. In the magnetic field H =H_y the MR can both increase and reduce and it always remains non‐negative when the thickness decreases.