Influence of dislocation microstructure on low temperature magnetoresistance in copper single- and polycrystals

Angular and field dependent transverse magnetoresistance (TMR) have been studied in copper single- and polycrystals containing different density and distribution of dislocations. In the open-orbit orientation, the quadratic variation of TMR with the applied magnetic field changes to the quasi-linear dependence, as the density of dislocations increases. In the closed-orbit orientations, TMR shows a linear dependence with the magnetic field, the slope of the characteristic decreases with increasing the density of dislocations. The signatures of closed and extended orbits are preserved until the very high dislocation densities stored in the single crystals. The analysis of the Kohler's plots indicates that in the open-orbit orientation TMR violates Kohler's rule, but in the closed-orbit orientation Kohler's rule is obeyed. The results suggest that at low dislocation density, the magneto-transport of electrons is strongly anisotropic and is dominated by small-angle scattering, irrespective of the distribution of dislocations. In the crystals with higher densities of dislocations containing dislocation walls and cells, the electron transport is dominated by a high-angle scattering process. The magnetoresistance data are consistent with the two-band model and support the theory that the dislocation-induced relaxation time is anisotropic due to the non-sphericity of the Fermi surface. In the spherical portion of the Fermi surface the scattering is isotropic, associated with the constant relaxation time. Strongly anisotropic scattering in the aspherical portion of the Fermi surface is associated with a much smaller relaxation time.