▎ 摘　　要

By simulating spin transport through graphene nanoscale junctions, which have been fabricated recently, we show that the junction can conduct a spin-polarized current even without an external field. Conduction through the conduction subband results in an opposite type of spin filtering from conduction through the valence subband. The junction is magnetic with a nonzero total spin that depends on the junction geometry. The qualitative conclusions remain the same no matter a one-side armchair edge junction or a zigzag edge junction is considered.