Negative magneto resistance in carbon nanotubes: A first principle study

We have studied spin transport through single wall carbon nanotube (SWNT) with nickel contacts using \textit{ab initio} density functional theory and green's function based Landauer B\"{u}ttiker formalism. Our results show enhanced current for anti-parallel alignment compared to that obtained for parallel alignment. This non Julli\'{e}re's model results due to finite size effect and this talk will present a detailed atomic level mechanism of such phenomena. Our results will be discussed in the light of recent experimental studies.