Theoretical investigation on spin-polarized junctions with 4-valued conductances: application to carbon nanotube encapsulating magnetic atoms

We theoretically investigate multiple-valued cell property in spin-polarized junctions, which is in principle realized by sensing conductances of four states recorded with magnetization configurations of two ferromagnets (FMs); (up,up), (up,down), (down,up), (down,down). Then, in order to sense all the states, 4-valued conductances corresponding to the respective states are necessary. Paying attention to the magnitude of magnetization in the whole system, we propose FM1/spin-polarized spacer (SPS)/FM2 junctions, where FM1 and FM2 have different spin polarizations, and the spacer depends on spin. In actual calculations, the FM1/SPS/FM2 junctions explicitly exhibit 4-valued conductances. As a realistic SPS, we consider a single-walled armchair carbon nanotube encapsulating magnetic atoms. The obtained 4-valued conductances behaviors are understood by considering electronic states of the nanotube.