Effective Mass Ratio & positive colossal magnetoresistance of a   Nano-wire
  In the present work, a relation has been established between degree of polarization and effective mass ratio (EMR) and magnetoresistance (MR) of one-dimensional non-degenerate system (which can represent a nano-wire or a linear chain of atoms and molecules in one dimension) by using a non-degenerate Hubbard model, which includes diagonal and off-diagonal matrix elements of Coulomb interaction. EMR is one of the most important property, which provides information that how much itinerant the system is? Within the mean field approximation, it is found that, due to the presence of off-diagonal elements, the band narrowing effect dominates over the band splitting effect. The EMR varies with degree of polarization. EMR for majority (up spin) carriers decreases as magnetization increases below ferromagnetic transition temperature. MR decreases as system is cooled below the ferromagnetic transition temperature. A comparison of our results with existing experimental observations is made. 
Piyush Dua