Y. Kohama et al 2008 EPL 84 37005 doi:10.1209/0295-5075/84/37005
Y. Kohama1,2, Y. Kamihara3,4, S. Riggs1, F. F. Balakirev1, T. Atake2, M. Jaime1, M. Hirano3,4 and H. Hosono3,4
Show affiliationsThe electrical resistivity and Hall coefficient of LaFeAsO0.95F0.05 polycrystalline samples were measured in pulsed magnetic fields up to μ0H=60 T from room temperature to 1.5 K. The resistance of the normal state shows a negative temperature coefficient (dρ/ dT<0) below 70 K for this composition, indicating insulating ground state in underdoped LaFeAsO system in contrast to heavily doped compound. The charge carrier density obtained from Hall effect can be described as constant plus a thermally activated term with an energy gap ΔE=630 K. The upper critical field, Hc2, estimated from resistivity measurements, exceeds 75 T with zero-field Tc=26.3 K, suggesting an unconventional nature for superconductivity.
74.70.-b Superconducting materials
74.25.Fy Transport properties (electric and thermal conductivity, thermoelectric effects, etc.)
Issue 3 (November 2008)
Received 24 June 2008, accepted for publication 23 September 2008
Published 24 October 2008
Y. Kohama et al 2008 EPL 84 37005
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