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Tunneling Magnetoresistance With Amorphous Electrodes



M Gradhand, Christian Heiliger, P Zahn, I Mertig


A detailed first principles analysis of the transport properties of different magnetic electrode materials for MgO tunnel junctions is performed to elucidate the microscopic origin of the TMR effect. The spin-dependent transport properties of the magnetic materials are analyzed separately from the particular interface geometry with the tunneling barrier. We use the bulk properties of the barrier to identify the important tunneling states. For MgO these are D1-like states. From the analysis of this effective spin polarization we can predict the potential of certain magnetic materials to create a high TMR ratio in a tunnel junction. This polarization is as high as 98 % and 86 % for Fe and Co, respectively for only a few monolayers, but very small and negative, -7 %, for amorphous Fe.This explains the finding that for crystalline Co and Fe one monolayer next to the MgO barrier is sufficient to reach TMR ratios higher than 500 % independent of whether the crystalline monolayer is coupled to a non-magnetic or to an amorphous lead. However, in direct contact with MgO amorphous Fe reduces the TMR ratio drastically to 44 %.
Physical Review B (Condensed Matter and Materials Physics)


amorphous electrodes, ballistic transport, coherent transport, Fe/MgO/Fe, tunnel junction, tunneling magnetoresistance


Gradhand, M. , Heiliger, C. , Zahn, P. and Mertig, I. (2007), Tunneling Magnetoresistance With Amorphous Electrodes, Physical Review B (Condensed Matter and Materials Physics), [online], (Accessed July 18, 2024)


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Created December 31, 2006, Updated October 12, 2021