Symposium P: Novel Aspects of Spintronic Materials and Devices

Symposium P, Novel Aspects of Spintronic Materials and Devices, provided an overview of challenges and recent progress in controlling the spin degrees of freedom in solid-state systems. It is instructive to think of a spintronics scheme as consisting of three different stages: generation of spin polarization, spin manipulation, and spin detection. Spin polarization can be defined as the ratio of the sum and the difference of spin-resolved components (spin-up and spin-down) of a particular quantity such as charge current, carrier density, or the density of states. While many materials in their ferromagnetic state can have a substantial degree of equilibrium carrier spin polarization, this alone is not sufficient for spintronic applications that typically require current flow and/or manipulation of the nonequilibrium spin (polarization). A large part of the symposium focused on the issues related to spin injection where, by driving electrical current across the interface between magnetic and nonmagnetic material, nonequilibrium spin polarization is introduced in a nonmagnetic material. Detailed theoretical considerations were presented by R.H. Silsbee (Cornell) and E.L Rashba (SUNY-Buffalo). Experimental reports on spin injection spanned a wide range of materials, from organic semiconductors (C. Taliani, ISM, Bologna, Italy) to HTSs (J. Wei, Univ. of Toronto). It was shown that metallic ferromagnets combined with a tunneling barrier can provide efficient room-temperature spin injection into common semiconductors such as GaAs (B.T. Jonker, NRL and V.I. Safarov, Univ. Aix-Marseille II, Marseille, France). An alternative method to inject spin into GaAs was discussed by S.S.P. Parkin (IBM Almaden Research Center). His technique employed a magnetic tunneling transistor, which is a three-terminal device combining a magnetic tunnel junction with a semiconductor collector. However, many materials challenges remain.