Магнитные и транспортные свойства кристаллов железосодержащих сверхпроводников семейств 122
Iron-based superconductors, just after their discovery in 2008, have become a subject of great interest for the scientific
community and occupy one of the leading places among the most topical subjects in contemporary solid-state physics. The present development of investigations of iron-containing superconductors can be compared perhaps with the great efforts to study properties of cuprate high-temperature superconductors (HTSCs) in the first years after their discovery. At present more than one hundred Fe-based superconductors of different compositions have been found. These compounds represent quite a new class of superconducting materials with crystal lattice containing ions of 3d metals (Fe, Co, Ni) well known as ferromagnetic metals. Therefore, a priori, other mechanism of superconducting pairing in Fe-based superconductors, different from the traditional electron±phonon coupling, cannot be ruled out. A characteristic feature of all iron-containing superconduc-
tors is the presence in their crystal structure of FeAs layers in the case of pnictides or FeSe layers in the case of
chalcogenides. At present, the maximum critical temperature Tc of the superconducting transition in Fe-based super-
conductors reaches 56 K (in a Gd1-xThxFeAsO compound), which is inferior only to Tc of cuprate HTSCs. This
circumstance undoubtedly makes it possible to place ironbased superconductors in the class of HTSCs.