‍‍‍‍‍‍‍‍‍‍主 讲：边秋平

时 间：11月17日下午 16：00—17：20

地 点：物电学院204会议室（理工北楼）

主 办：淮阴师范学院科技处 物电学院

主讲人简介：Dr. Qiuping Bian, Research Associate(PDF), Department of MaterialsScience and Engineering, McMaster University, Canada.

主要内容：Thedescription of the electron transport in the presence of lattice dislocationshas encountered difficulties related to the understanding the nature of electron-dislocationcollisions. As for now, there is no universal theory capable to predict thebehavior of the electrons in the metal containing different types ofdislocation microstructure under the influence of the applied magnetic field. Inthe present studies, the angular and field dependent transverse magnetoresistance(TMR) of deformed copper single- and poly-crystals has been investigated. Ithas been found that in the open-orbit orientation, the quadratic variation ofTMR with the applied magnetic field changes to the quasi-linear dependence, asthe density of dislocations increases. In the closed-orbit orientations, TMRshows a linear dependence with the applied field, the slope of thecharacteristic decreases with increasing the density of dislocations. Thesignatures of the closed and extended orbit configurations are preserved tillthe very high dislocation densities stored in the single crystals. The analysisof the Kohler's plots indicates that in the open orbit orientations thecrystals violate the Kohler's rule, but in the closed-orbit orientation theKohler's rule is obeyed. The results suggest that in the single crystalscontaining low dislocation density, the magneto-transport of electrons isstrongly anisotropic and is dominated by the small-angle scattering,irrespective of the distribution of dislocations. In the crystals containinghigher density of dislocations, due to the entanglement of dislocations and theformation of dislocation walls and cells, the electron transport is dominatedby large-angle scattering processes. A theoretical model based on the effectivemedium theory has been developed to simulate the experimental measurements ofTMR. The model incorporates two energy bands with the different relaxation timeand takes into account of the characteristic features of dislocation microstructureintroduced during deformation. The talk will provide basis for the discussionof fundamental aspects of magneto-transport of conductive electrons in puremetals and in metals with dislocation microstructure.

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