Abstract
Superconducting phases of have been synthesized by the intercalation of metal atoms into FeSe and using a low-temperature liquid technique. The superconducting transition temperature is 31.5 K for Na-doped FeSe, and for Li-, Na-, and Ca-doped it is 26, 22, and 17 K, respectively. The 31.5 K superconducting is the superconducting phase in ammoniated Na-doped FeSe. The is lower than that (onset of the superconducting phase reported previously. The reason why the of this phase is lower is discussed based on the structure. The pressure dependences of in the and samples have been measured and a negative pressure dependence is observed; i.e., a decrease in lattice constant leads to a decrease in , consistent with the behavior of reported previously by our group. Furthermore, the magnetic behavior of has been fully investigated at different applied magnetic fields ) to determine the critical magnetic field. This is a successful metal intercalation into and an observation of superconductivity.
- Received 4 February 2014
- Revised 1 April 2014
DOI:https://doi.org/10.1103/PhysRevB.89.144509
©2014 American Physical Society