Letter abstract
Nature Materials 8, 630 - 633 (2009)
Published online: 14 June 2009 | doi:10.1038/nmat2491
Subject Categories: Magnetic materials | Superconductors
Electronic and magnetic phase diagram of 
-Fe1.01Se with superconductivity at 36.7 K under pressure
S. Medvedev1,2, T. M. McQueen3, I. A. Troyan2,4, T. Palasyuk2,5, M. I. Eremets2, R. J. Cava3, S. Naghavi1, F. Casper1, V. Ksenofontov1, G. Wortmann6 & C. Felser1
The discovery of new high-temperature superconductors1 based on FeAs has led to a new 'gold rush' in high-TC superconductivity. All of the new superconductors share the same common structural motif of FeAs layers and reach TC values up to 55 K (ref. 2). Recently, superconductivity has been reported in FeSe (ref. 3), which has the same iron pnictide layer structure, but without separating layers. Here, we report the magnetic and electronic phase diagram of 
-Fe1.01Se as a function of temperature and pressure. The superconducting transition temperature increases from 8.5 to 36.7 K under an applied pressure of 8.9 GPa. It then decreases at higher pressures. A marked change in volume is observed at the same time as TC rises, owing to a collapse of the separation between the Fe2Se2 layers. No static magnetic ordering is observed for the whole p–T phase diagram. We also report that at higher pressures (starting around 7 GPa and completed at 38 GPa), Fe1.01Se transforms to a hexagonal NiAs-type structure and exhibits non-magnetic behaviour.
- Institut für Anorganische und Analytische Chemie, University Mainz, 55099 Mainz, Germany
- Max-Planck-Institute for Chemistry, 55128 Mainz, Germany
- Department of Chemistry, Princeton University, Princeton New Jersey 08544, USA
- A.V. Shubnikov Institute of Crystallography, 119333 Moscow, Russia
- Institute of Physical Chemistry PAS, Warsaw 01-224, Poland
- Department Physik, Universität Paderborn, 33095 Paderborn, Germany
Correspondence to: C. Felser1 e-mail: felser@uni-mainz.de
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