Giant magnetoresistance effect and spin filters in phthalocyanine-based molecular devices

Abstract

The spin transport properties of molecular devices constructed by hydrogen–phthalocyanine and transition metal (TM)–phthalocyanine molecule with zigzag graphene nanoribbon electrodes are investigated by the Keldysh nonequilibrium Green’s function method in combination with the density functional theory. The results show that there exists giant magnetoresistance in both the hydrogen–phthalocyanine and the TM-phthalocyanine systems. The magnetoresistance ratio is much bigger than that found by Schmaus et al. [S. Schmaus, A. Bagrets, Y. Nahas, T. K. Yamada, A. Bork, M. Bowen, E. Beaurepaire, F. Evers, W. Wulfhekel, Nature Nanotechnology 6 (2011) 185–9] in single hydrogen–phthalocyanine-Co electrodes system. Moreover, it is found that the chromium–phthalocyanine molecular device is a good spin filtering device with nearly 100% spin filtering efficiency at a wide bias voltage region. The mechanisms are proposed for these phenomena.