Giant magnetoresistance (GMR) denotes a large change in the electrical resistance under the application of a magnetic field and the GMR effect observed in magnetic metallic multilayers (MMM) has now become the canonical GMR effect since it transformed the magnetic hard disk storage and memory industries. Although not as well known, GMR also occurs in both magnetic and non-magnetic semiconductor systems. Semiconductor GMR is particularly interesting for applications because of the expected ease of integration of associated devices with typical semiconductor electronics. As a consequence, the study of potential new mechanisms for realizing GMR in semiconductors has been a useful line of basic research. Here, we report the results of an experimental study that aimed to examine and model an interesting giant magnetoresistance effect in the GaAs/AlGaAs system, an effect which shows strong sensitivity to the size of the device and also a dc-biasing current.[1,2] The size dependent study shows that a ''bell-shape'' negative GMR grows in magnitude with decreasing temperatures as the span of this magnetoresistance on the magnetic-field-axis increases with decreasing device width, W. Remarkably, measurements do not show concurrent Hall resistance, Rxy, correction. The current bias study shows that at a fixed temperature, the magnitude of the GMR can be tuned with the supplemental dc current. A multi-conduction model, including negative diagonal conductivity, and non-vanishing off-diagonal conductivity,reproduces observed experimental magnetoresistance traces. The significance of the negative conductivity term, and the non-vanishing off-diagonal conductivity, in the modeling of the observations, will be discussed.[1,2]
 R. G. Mani et al., Nature-Scientific Reports, 3, 2747 (2013).