Iron with a large magnetic moment was widely believed to be harmful to the
emergence of superconductivity because of the competition between the static
ordering of electron spins and the dynamic formation of electron pairs (Cooper
pairs). Thus, the discovery of a high critical temperature (Tc) iron-based
superconductor (IBSC) in 2008 was accepted with surprise in the condensed
matter community and rekindled extensive study globally. IBSCs have since grown
to become a new class of high-Tc superconductors next to the high-Tc cuprates
discovered in 1986. The rapid research progress in the science and technology
of IBSCs over the past decade has resulted in the accumulation of a vast amount
of knowledge on IBSC materials, mechanisms, properties, and applications with
the publication of more than several tens of thousands of papers. This article
reviews recent progress in the technical applications (bulk magnets, thin
films, and wires) of IBSCs in addition to their fundamental material
characteristics. Highlights of their applications include high-field bulk
magnets workable at 15-25 K, thin films with high critical current density (Jc)
> 1 MA/cm2 at ~10 T and 4 K, and an average Jc of 1.3*104 A/cm2 at 10 T and 4 K
achieved for a 100-m-class-length wire. These achievements are based on the
intrinsically advantageous properties of IBSCs such as the higher
crystallographic symmetry of the superconducting phase, higher critical
magnetic field, and larger critical grain boundary angle to maintain high Jc.
These properties also make IBSCs promising for applications using high magnetic
fields.Comment: Published online in Materials Today. Open Acces