Regensburg 2002 – wissenschaftliches Programm
SYSP IV.1: Hauptvortrag
Donnerstag, 14. März 2002, 11:00–11:30, H1
Spin Polarized Tunneling - The Evolution — •Jagadeesh Moodera — Francis Bitter Magnet Laboratory, MIT, Cambridge, MA 02139, USA
The field of spin polarized tunneling has blossomed into an active area of study especially so in the last several years. The catalyst for this sudden intensity of research comes from the high application potential for the magnetic tunnel junctions. Meservey and Tedrow discovered (1971) in their pioneering experiments that tunneling electrons coming from a ferromagnet are spin polarized and that the spin is conserved in the tunneling process. The origin and sign of spin polarization from transition metal ferromagnets (FM) and alloys measured by this spin polarized tunneling technique using a superconducting Al has been investigated for nearly three decades - a subject of intense discussion, theoretically and experimentally. Where does the basic polarization arise? How do the spin up/down wave functions decay in the barrier? Although it is believed that spin polarization measured in tunneling experiments to be widely dominated by 4s states that are further extended in space, the contribution of the FM-3d states to the tunneling current can be expected. Understanding this can lead to the possibility of engineering the right interface material which can be expected to show even higher spin polarization. The state of these issues will be reviewed and discussed. Work supported by NSF and ONR grants. . R. Meservey and P. M. Tedrow, Phys. Rept., 238, 173 (1994). J. S. Moodera, J. Nassar and G. Mathon, Annu. Rev. Mater. Sci. 29, 381 (1999). P. LeClair, J. T. Kohlhepp, H. J. M. Swagten and W. J. M. de Jonge, PRL 86 1066 (2001). I. I. Oleinik, E. Y. Tsymbol and D. G. Pettifor, PR B62, 3952 (2000). A. H. Davis and J. MacLaren, JAP 87, 5224 (2000). W. H. Butler, X. G. Zhang, T. C. Schulthess, et al. PR B63, 2402 (2001).