Perfect spin-filter and spin-valve in carbon atomic chains

We report ab initio calculations of spin-dependent transport in single atomic carbon chains bridging two zigzag graphene nanoribbon electrodes. Our calculations show that carbon atomic chains coupled to graphene electrodes are perfect spin-filters with almost 100% spin polarization. Moreover, the carbon atomic chains show bias-dependent magnetoresistance as large as 10(6)% which make them perfect spin-valves. These two spin-related properties are independent of the length of carbon chains. The simultaneous occurrence of spin-filter and spin-valve in a single device opens the possibilities of all-carbon composite spintronics.