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Tuning spin transport properties and molecular magnetoresistance through contact geometry
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF. KTH, Centres, SeRC - Swedish e-Science Research Centre.ORCID iD: 0000-0001-7788-6127
2014 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 140, no 4, 044716- p.Article in journal (Refereed) Published
Abstract [en]

Molecular spintronics seeks to unite the advantages of using organic molecules as nanoelectronic components, with the benefits of using spin as an additional degree of freedom. For technological applications, an important quantity is the molecular magnetoresistance. In this work, we show that this parameter is very sensitive to the contact geometry. To demonstrate this, we perform ab initio calculations, combining the non-equilibrium Green's function method with density functional theory, on a dithienylethene molecule placed between spin-polarized nickel leads of varying geometries. We find that, in general, the magnetoresistance is significantly higher when the contact is made to sharp tips than to flat surfaces. Interestingly, this holds true for both resonant and tunneling conduction regimes, i.e., when the molecule is in its "closed" and "open" conformations, respectively. We find that changing the lead geometry can increase the magnetoresistance by up to a factor of similar to 5. We also introduce a simple model that, despite requiring minimal computational time, can recapture our ab initio results for the behavior of magnetoresistance as a function of bias voltage. This model requires as its input only the density of states on the anchoring atoms, at zero bias voltage. We also find that the non-resonant conductance in the open conformation of the molecule is significantly impacted by the lead geometry. As a result, the ratio of the current in the closed and open conformations can also be tuned by varying the geometry of the leads, and increased by similar to 400%.

Place, publisher, year, edition, pages
2014. Vol. 140, no 4, 044716- p.
Keyword [en]
Single-Molecule, Carbon Nanotube, Conductance, Junctions, Spintronics, Devices, Switch
National Category
Other Physics Topics
URN: urn:nbn:se:kth:diva-142885DOI: 10.1063/1.4862546ISI: 000331211700086ScopusID: 2-s2.0-84902156078OAI: diva2:705033
Swedish Research CouncilKnut and Alice Wallenberg FoundationSwedish eā€Science Research Center

QC 20140314. Correction in: Journal of Chemical Physics, vol. 140, issue. 22, article nr. 229903, doi: 10.1063/1.4883490, WOS:000337806100056

Available from: 2014-03-14 Created: 2014-03-13 Last updated: 2014-08-14Bibliographically approved

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Delin, Anna
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