Multiple Phase Transitions in Single-Crystalline Na1-δFeAs
G. F. Chen, W. Z. Hu, J. L. Luo, and N. L. Wang
(Received 21 February 2009; published 4 June 2009)
Specific heat, resistivity, susceptibility, and Hall coefficient measurements were performed on highquality single-crystalline Na1-δFeAs. This compound is found to undergo three successive phase transitions at around 52, 41, and 23 K, which correspond to structural, magnetic, and superconducting transitions, respectively. The Hall effect result indicates the development of energy gap at low temperature due to the occurrence of spin-density-wave instability. Our results provide direct experimental evidence of the magnetic ordering in the nearly stoichiometric NaFeAs.
PACS numbers: 74.70.-b, 74.25.Fy, 74.25.Gz