High-temperature antiferromagnetism in molecular semiconductor thin films and nanostructures.
The viability of dilute magnetic semiconductors in applications is linked to the strength of the magnetic couplings, and room temperature operation is still elusive in standard inorganic systems. Molecular semiconductors are emerging as an alternative due to their long spin-relaxation times and ease of processing, but, with the notable exception of vanadium-tetracyanoethylene, magnetic transition temperatures remain well below the boiling point of liquid nitrogen. Here we show that thin films and powders of the molecular semiconductor cobalt phthalocyanine exhibit strong antiferromagnetic coupling, with an exchange energy reaching 100 K. This interaction is up to two orders of magnitude larger than in related phthalocyanines and can be obtained on flexible plastic substrates, under conditions compatible with routine organic electronic device fabrication. Ab initio calculations show that coupling is achieved via superexchange between the singly occupied a1g () orbitals. By reaching the key milestone of magnetic coupling above 77 K, these results establish quantum spin chains as a potentially useable feature of molecular films.
1] Department of Materials, Imperial College London, London SW7 2AZ, UK [2] London Centre for Nanotechnology, Imperial College London, London SW7 2AZ, UK.
Michele
M
Serri
1] Department of Materials, Imperial College London, London SW7 2AZ, UK [2] London Centre for Nanotechnology, Imperial College London, London SW7 2AZ, UK [3] Department of Chemistry, Imperial College London, London SW7 2AZ, UK.
Wei
W
Wu
1] Department of Materials, Imperial College London, London SW7 2AZ, UK [2] London Centre for Nanotechnology, Imperial College London, London SW7 2AZ, UK.
Luke R
LR
Fleet
1] London Centre for Nanotechnology, Imperial College London, London SW7 2AZ, UK [2] Department of Chemistry, Imperial College London, London SW7 2AZ, UK.
Nicholas M
NM
Harrison
1] London Centre for Nanotechnology, University College London, London WC1E 6BT, UK [2] Department of Chemistry, University College London, London WC1E 6BT, UK [3] Department of Physics and Astronomy, University College London, London WC1E 6BT, UK.
Cyrus F
CF
Hirjibehedin
1] London Centre for Nanotechnology, University College London, London WC1E 6BT, UK [2] Institute of Structural and Molecular Biology, University College London, London WC1E 6BT, UK.
Christopher W M
CW
Kay
1] London Centre for Nanotechnology, University College London, London WC1E 6BT, UK [2] Department of Physics and Astronomy, University College London, London WC1E 6BT, UK.
Andrew J
AJ
Fisher
1] London Centre for Nanotechnology, University College London, London WC1E 6BT, UK [2] Department of Physics and Astronomy, University College London, London WC1E 6BT, UK.
Gabriel
G
Aeppli
1] Department of Materials, Imperial College London, London SW7 2AZ, UK [2] London Centre for Nanotechnology, Imperial College London, London SW7 2AZ, UK.
Sandrine
S
Heutz