The Electronic Structures of Fullerene/Transition-Metal Hybrid Material
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1081-P07-01
The Electronic Structures of Fullerene/Transition-Metal Hybrid Materia Yoshihiro Matsumoto1, Seiji Sakai1, Hiroshi Naramoto2, Norie Hirao3, Yuji Baba3, Isamu Sugai4, Koki Takanashi4, Shimada Toshihiro5, and Yoshihito Maeda6 1 Advanced Science Research Center, Japan Atomic Energy Agency, 2-4 Shirakata Shirane, Tokai, Naka, 319-1195, Japan 2 Radiation Application Development Association, Tokai, Naka, 319-1195, Japan 3 Synchrotron Radiation Center, Japan Atomic Energy Agency, 2-4 Shirakata Shirane, Tokai, Naka, 319-1195, Japan 4 Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 9808577, Japan 5 Department of Chemistry, Tokyo Uviversity, Hongo, Bunkyo-ku, Tokyo, 113-8654, Japan 6 Department of Energy Science and Technology, Kyoto University, Sakyo-ku, Kyoto, 606-8501, Japan ABSTRACT Local electronic structures of C60-Co hybrid films have been studied by X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. XPS spectra of C 1s main and satellite peaks for the C60-Co films show bindingenergy shifts and also line-broadening compared to those in a pure C60 film. In addition, XPS spectra in valence band region suggest an appearance of three new components at near Fermi level and HOMO level in the C60-Co film. These results are attributed to hybridizations between Co 3d band and C60 π* molecular orbital with a charge transfer from Co atom to C60 molecule. The same effects have been observed in NEAXFS spectra at C 1s excitations.
INTRODUCTION Molecular-spintronics is a new and promising research field where organic substances such as carbon nanotube (CNT), fullerene (C60) and organic molecules which contain carbonhydrogen bonds are employed to mediated or control a spin-polarized signal [1]. It is only recently that spin has entered the field of molecular electronics. The driving idea behind the first pioneering experiment of Tsukagoshi and coworkers [2], who injected spin-polarized electrons into CNT, is that spin-orbit interactions are very weak in carbon-based substances. In addition to the rather weak hyperfine interactions, this fact suggests extremely long spin relaxation times, and therefore the possibility of coherent spin propagation over large distances is expected. A rather conservative estimate of the spin diffusion length from the Tsukagoshi’s experiment indicated 130 nm as a lower bound of the spin-diffusion in CNT. These findings have stimulated growing activities in the area, and several experiments dealing with molecular tunneling junctions [3], spin-transport through polymers [4-6] and optical pump/probe experiments through molecular bridges [7] have been induced. On the other hand, under these circumstances, the considerably high (5-40%) magnetoresistance (MR) ratio has been reported in the hybrid systems of organic molecules and ferromagnetic transition metals, even if it is still low compared with the theoretical predictions [8,9].
Very recently, we have found that C60 and Co hybrid films where Co nano
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