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Electronic structure of thin film cobalt tetracyanoethylene, Co(TCNE)x
Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
MESA Institute for Nanotechnology, University of Twente, 7500 AE Enschede, The Netherlands.
Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
2010 (English)In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 161, no 17-18, 1892-1897 p.Article in journal (Refereed) Published
Abstract [en]

V(TCNE)x, TCNE=tetracyanoethylene, x~2, is a semiconducting organicbased magnet and one of very few organic-based magnets with critical temperature above room temperature (RT). With the aim to understand the key design criteria for achieving RT organic-based magnets we have started to study the electronic and chemical structure of members of the M(TCNE)x family with significantly lower critical temperatures than V(TCNE)x. In this paper, Co(TCNE)x, x~2, (Tc~44 K, derived from its powder form) were prepared by a method based on physical vapor deposition, resulting in oxygen-free thin films. The results propose Co(TCNE)x to contain to local bonding disorder in contrast to V(TCNE)x thin films, which can be grown virtually defect free. In addition, the Co L-edge does not show any pronounced fine structure, suggesting the crystal field to be very weak. By using a variety of photoemission and X-ray absorption techniques the highest occupied molecular orbital (HOMO) of Co(TCNE)x was determined to mainly be TCNE-derived while the states originating from Co(3d) are localized at higher binding energies. This is in stark contrast to V(TCNE)x where V(3d) is mainly responsible for the HOMO. As the HOMO of Fe(TCNE)x (Tc~121 K, derived from its powder form) is TCNE-derived these results show that Co(TCNE)x is more similar to Fe(TCNE)x than to V(TCNE)x in terms of electronic structure.

Place, publisher, year, edition, pages
Elsevier , 2010. Vol. 161, no 17-18, 1892-1897 p.
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:liu:diva-56261DOI: 10.1016/j.synthmet.2011.06.031ISI: 000295564000016OAI: oai:DiVA.org:liu-56261DiVA: diva2:317831
Note

Funding agencies|Swedish Research Council||Knut and Alice Wallenberg Foundation||

Available from: 2010-05-05 Created: 2010-05-05 Last updated: 2017-12-12
In thesis
1. Development of Organic-Based Thin Film Magnets for Spintronics
Open this publication in new window or tab >>Development of Organic-Based Thin Film Magnets for Spintronics
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In the growing field of spintronics, development of semiconducting magnets is a high priority. Organic-based molecular magnets are attractive candidates since their properties can be tailor-made by organic chemistry. Other advantages include low weight and low temperature processing. Vanadium tetracyanoethylene, V(TCNE)x, x~2, is particularly interesting since it is one of very few semiconducting magnets with magnetic ordering above room temperature.

The aim of the research presented in this thesis was to prepare and characterize thin film organic-based magnets with focus on V(TCNE)x. Photoelectron and absorption spectroscopy studies were performed leading to a more complete picture of the electronic and chemical structure of the material. Depending on the preparation method of V(TCNE)x, the material contains varying amounts of disorder which among other things makes it very air sensitive. In this thesis, a new preparation method for organic-based magnets based on physical vapor deposition is presented and the first result shows that it generates less air sensitive V(TCNE)x than previous methods reported. A new spin valve design based on V(TCNE)x was proposed where the material delivers both spin-filtering and spin-transporting functionality, making use of its fully spin-polarized transport levels. In such devices, the interface of V(TCNE)x with ferromagnetic metals is of great importance and was hence studied. As vanadium ions always are very reactive towards oxygen, substituting vanadium by a less reactive ion would be desirable from both an interface engineering and device packaging perspective. Very few alternatives exist however that orders magnetically above room temperature. In order to find out what are the key design criteria for preparing thin film semiconducting room temperature magnets, we have begun to study systems which order magnetically much below room temperature and compared them with V(TCNE)x.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2010. 49 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1317
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-56262 (URN)978-91-7393-385-8 (ISBN)
Public defence
2010-05-25, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
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Available from: 2010-05-05 Created: 2010-05-05 Last updated: 2010-05-05Bibliographically approved

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Carlegrim, ElinZhan, YiqiangFahlman, Mats

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