Dept. of Physics and Astronomy, Georgia State University, Atlanta, GA 30303 U.S.A.
Sci Rep. 2013 Sep 25;3:2747. doi: 10.1038/srep02747.
Large changes in the electrical resistance induced by the application of a small magnetic field are potentially useful for device-applications. Such Giant Magneto-Resistance (GMR) effects also provide new insights into the physical phenomena involved in the associated electronic transport. This study examines a "bell-shape" negative GMR that grows in magnitude with decreasing temperatures in mm-wide devices fabricated from the high-mobility GaAs/AlGaAs 2-Dimensional Electron System (2DES). Experiments show that the span of this magnetoresistance on the magnetic-field-axis increases with decreasing device width, W, while there is no concurrent Hall resistance, Rxy, correction. A multi-conduction model, including negative diagonal-conductivity, and non-vanishing off-diagonal conductivity, reproduces experimental observations. The results suggest that a size effect in the mm-wide 2DES with mm-scale electron mean-free-paths is responsible for the observed "non-ohmic" size-dependent negative GMR.
由小磁场引起的电阻的大幅变化对于器件应用具有潜在的用处。这种巨磁电阻（GMR）效应也为相关电子输运中涉及的物理现象提供了新的见解。本研究考察了来自高迁移率 GaAs/AlGaAs 二维电子系统（2DES）的毫米宽器件中出现的“钟形”负 GMR，其在低温下的幅度随磁场减小而增大。实验表明，在磁场轴上，这种磁电阻的跨度随器件宽度 W 的减小而增大，而霍尔电阻 Rxy 没有相应的校正。一个包括负对角电导率和非零非对角电导率的多传导模型再现了实验观察结果。结果表明，在具有毫米级电子平均自由程的毫米宽 2DES 中存在尺寸效应，这导致了观察到的非欧姆尺寸相关的负 GMR。
