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Electronic structure of thin film iron-tetracyanoethylene: Fe(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.
Adam Mickiewicz University Poznan.
University of Twente.
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2009 (English)In: Applied Physics A: Materials Science & Processing, ISSN 0947-8396, E-ISSN 1432-0630, Vol. 95, no 1, 131-138 p.Article in journal (Refereed) Published
Abstract [en]

Thin film iron-tetracyanoethylene Fe(TCNE) x , x∼2, as determined by photoelectron spectroscopy, was grown in situ under ultra-high vacuum conditions using a recently developed physical vapor deposition-based technique for fabrication of oxygen- and precursor-free organic-based molecular magnets. Photoelectron spectroscopy results show no spurious trace elements in the films, and the iron is of Fe2+ valency. The highest occupied molecular orbital of Fe(TCNE) x is located at ∼1.7 eV vs. Fermi level and is derived mainly from the TCNE singly occupied molecular orbital according to photoelectron spectroscopy and resonant photoelectron spectroscopy results. The Fe(3d)-derived states appear at higher binding energy, ∼4.5 eV, which is in contrast to V(TCNE)2 where the highest occupied molecular orbital is mainly derived from V(3d) states. Fitting ligand field multiplet and charge transfer multiplet calculations to the Fe L-edge near edge X-ray absorption fine structure spectrum yields a high-spin Fe2+ (3d6) configuration with a crystal field parameter 10Dq∼0.6 eV for the Fe(TCNE) x system. We propose that the significantly weaker Fe-TCNE ligand interaction as compared to the room temperature magnet V(TCNE)2 (10Dq∼2.3 eV) is a strongly contributing factor to the substantially lower magnetic ordering temperature (T C ) seen for Fe(TCNE) x -type magnets.

Place, publisher, year, edition, pages
2009. Vol. 95, no 1, 131-138 p.
National Category
Natural Sciences
URN: urn:nbn:se:liu:diva-17167DOI: 10.1007/s00339-008-5032-yOAI: diva2:202156
Available from: 2009-03-07 Created: 2009-03-07 Last updated: 2015-05-18
In thesis
1. Fabrication and study of inorganic and organic thin film magnets
Open this publication in new window or tab >>Fabrication and study of inorganic and organic thin film magnets
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Thin film magnets are very important for many kinds of electronic devices and play a crucial role to achieve optimum performance. Therefore an intense level of research is going on all around the world to fabricate advanced electronics devices using both new inorganic and organic thin-film magnets. Historically, most magnetic materials used for technological applications are based on inorganic materials and have been studied extensible up to now. Recently, however, organic or molecular magnets have opened a new prospective of thin film magnets which have begun to show promise, offering the possibility of light-weight flexible materials and devices that include magnetic functionality.

The research presented in this thesis is hence divided into two parts, where inorganic and organic magnets in thin films form were studied. The Ti/Ni multilayer system is studied as an inorganic magnet in the first part, whereas M(TCNE)x thin films were studied in the second part with M= Fe, Ni and TCNE is tetracynoethelene, an organic compound, and x~2.

The Ti/Ni multilayer is a potential candidate for industrial applications and also features solid-state amorphisation. Because of various interesting scientific and technological aspects of Ti/Ni multilayer structures, many structural properties and subsequent thermal stability studies have been extensively reported in the literature, but surprisingly few reports are available on the corresponding electronic and magnetic properties. The work in the present thesis is therefore focused on synthesis and systematic investigation of structural, electronic and magnetic properties of as prepared as well as annealed Ti/Ni multilayer structures and to establish correlation between them.

The second part of the thesis deals with organic-based molecular magnets of the M(TCNE)x type, where x~2, M = Fe, Ni and TCNE = tetracynoethelene. Fe(TCNE)x and Ni(TCNE)x have for the first time been fabricated as thin films, free of oxygen- and precursor-induced defects. The films were fabricated in situ under ultra high vacuum conditions using our group’s recently developed fabrication techniques for organic-based molecular magnets. The previously unknown electronic structure of these thin film magnets are presented in the thesis. Room temperature magnetic ordering was observed for thin films of Ni(TCNE)2, in stark contrast to earlier versions of the material (fabricated with the old methods and hence containing various defects). Room temperature magnetic ordering for a similar system, Ni2(TCNE), previously has been reported by another group, but it is clear that more studies are necessary to completely resolve the underlying mechanisms for the magnetic properties seen in these materials.

Place, publisher, year, edition, pages
Linköping: Institutionen för teknik och naturvetenskap, 2007. 65 p.
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1152
Physics, electronic, thin films, inorganic magnets, organic magnets
National Category
Physical Sciences
urn:nbn:se:liu:diva-11442 (URN)978-91-85895-20-5 (ISBN)
Public defence
2007-12-14, K3, Kåkenhus, Campus Norrköping, Linköpings universitet, Norrköping, 10:15 (English)
Available from: 2008-04-01 Created: 2008-04-01 Last updated: 2012-11-21

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