Transport properties of transition-metal-encapsulated Si cages*

We performed density functional pseudopotential calculations of the spin dependent transport through transition-metal-atom-encapsulated Si cages Si$_{12}X$($X$=Mn, Fe and Co). The effect of the metal atom on conductance is studied. Mn and Fe doped systems show highly spin polarized transmission whereas the magnetization in Co doped system is quenched. It is found that electrons are transferred from Si atoms into the minority $d$ orbitals of the metal atoms. The conductance decreases as these electrons become localized around the encapsulated atoms.