Superconductivity at 15.6 K in calcium-doped Tb1-xCaxFeAsO: The structure requirement for achieving superconductivity in the hole-doped 1111 phase
National Laboratory for Superconductivity, Institute of Physics and Beijing National Laboratory for Condensed Matter Physics, Chinese Academy of Sciences - P. O. Box 603, Beijing 100190, PRC
Corresponding author: firstname.lastname@example.org
Accepted: 21 December 2009
Superconductivity at about 15.6 K was achieved in Tb1-xCaxFeAsO by partially substituting Tb3+ with Ca2+ in the nominal doping region x = 0.40–0.50. A detailed investigation was carried out on a typical sample with doping level of x = 0.44. The upper critical field of this sample was estimated to be 77 T from the magnetic–field–dependent resistivity data. The domination of hole-type charge carriers in the low-temperature region was confirmed by Hall effect measurements. The comparison between the calcium-doped sample Pr1-xCaxFeAsO (non-superconductive above 1.8 K) and the strontium-doped sample Pr1-xSrxFeAsO (superconductive) suggests that a lager ion radius of the doped alkaline-earth element compared with that of the rare-earth element may be a necessary requirement for achieving superconductivity in the hole-doped 1111 phase.
PACS: 74.10.+v – Occurrence, potential candidates / 74.70.Dd – Ternary, quaternary, and multinary compounds (including Chevrel phases, borocarbides, etc.) / 74.62.Dh – Effects of crystal defects, doping and substitution
© EPLA, 2010