Spin-dependent transport in films composed of Co clusters and C60 fullerenes

H. Zare-Kolsaraki; H. Micklitz

doi:10.1140/epjb/e2004-00244-4

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2024 Impact factor 1.7

Condensed Matter and Complex Systems

Eur. Phys. J. B 40, 103-109 (2004)
https://doi.org/10.1140/epjb/e2004-00244-4

Spin-dependent transport in films composed of Co clusters and C₆₀ fullerenes

H. Zare-Kolsaraki^a and H. Micklitz

II. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany

Corresponding author: ^a kolsarak@ph2.uni-koeln.de

Received: 17 March 2004
Published online: 3 August 2004

Abstract

Granular films of Co-cluster/C₆₀ mixtures have been prepared by the co-deposition of well defined Co clusters (mean diameter ≈4.5 nm) and C₆₀ fullerenes onto a cold (≈35 K) substrate. Films having a Co cluster volume fraction $0.23 \leq v_{\rm Co} \leq 0.32$ show a resistivity $\rho \propto \exp(T_{0}/T)^{1/2}$ , typical for tunneling with a Coulomb barrier. The tunneling magnetoresistance (TMR) has a value of TMR ( $T \rightarrow 0) = 33$ % for $v_{\rm Co} = 0.23$ and is decreasing by almost one order of magnitude going to $v_{\rm Co} = 0.32$ . We explain this unusual decrease of the TMR with increasing v_Co as caused by electron-doping of the C₆₀ fullerenes due to the known charge transfer process occurring between transition metal surface and C₆₀. Increasing electron doping may lead to an increasing probability for spin-flip processes within the tunneling barrier, resulting in a decrease of the TMR.