Regensburg 2007 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 6: Nanoelectronics III - Molecular Electronics

TT 6.10: Talk

Monday, March 26, 2007, 16:30–16:45, H19

Cotunneling and non-equilibrium magnetization in magnetic molecular monolayers — •Florian Elste¹ and Carsten Timm² — ¹Institut für Theoretische Physik, Freie Universität Berlin, Germany — ²Department of Physics and Astronomy, University of Kansas, USA

We study the interplay of electronic transport through monolayers of magnetic molecules and their non-equilibrium magnetic moment. A master-equation approach going beyond the sequential-tunneling approximation is applied to study the Coulomb-blockade regime. While the current is very small in this case, the magnetization can be switched by an amount of the order of the saturation magnetization by a small change of bias voltage, and without causing the flow of a large current. Inelastic cotunneling processes manifest themselves as steps in the differential conductance, which are accompanied by much larger changes in the magnetization. In addition, the magnetization in the Coulomb-blockade regime exhibits strong signatures of sequential-tunneling processes de-exciting molecular states populated by inelastic cotunneling. We also consider the case of a magnetic single-molecule transistor, finding that cotunneling processes lead to the occurrence of magnetic sidebands below the Coulomb-blockade threshold. In the context of spintronics applications, we investigate effects of additional spin relaxation. Our results show that sufficiently fast spin relaxation washes out the fine structure in the differential conductance and in the magnetization. At the same time, fast spin relaxation, while in general undesirable, can lead to a highly-polarized current in the presence of a magnetic field.