The level shifting induced negative magnetoresistance in the   nearest-neighbor hopping conduction
  We propose a new mechanism of negative magnetoresistance in non-magnetic granular materials in which electron transport is dominated by hopping between two nearest-neighbor clusters. We study the dependence of magnetoresistance on temperature and separation between neighboring clusters. At a small separation we find a negative magnetoresistance at low temperatures and it changes over to a positive value as temperature increases. For a fixed temperature, magnetoresistance changes from negative to positive when the cluster separation increases. The change of magnetoresistance $\Delta R/R$ can be more than 80% at low temperatures. 
X.R. Wang (1), S.C. Ma (1), X.C. Xie (2) ((1) The Hong Kong University   of Science and Technology, (2) Oklahoma State Unive...