Spin-current rectification in molecular wires

We propose that spin current rectification in molecular junctions can take two different forms consistent with thermodynamic considerations: A weak form in which the spin current reverses direction when the bias applied to the junction is reversed and a strong form in which the direction of the spin current is unchanged upon reversal of the bias. We present calculations of spin-dependent transport in several molecular junctions bridging ferromagnetic (Fe or Ni) and nonmagnetic (Au or Pd) contacts and identify specific systems that should exhibit spin current rectification of each type in appropriate ranges of the applied bias voltage. Our results indicate that molecular junctions displaying both spin-current and charge-current rectification should be possible, and may find practical application in nanoscale devices that combine logic and memory functions.