The 12442-type Fe-based superconductor
is the only system that
possesses two FeAs layers between neighboring insulating layers, which
is worth the in-depth investigations. In this work, millimeter-sized
single crystals of KCa2Fe4As4F2 were grown using a self-flux method. The chemical compositions
and crystal structure were characterized carefully. Superconductivity
with the critical transition T
c = 33.5
K was confirmed by both the resistivity and magnetic susceptibility
measurements. Moreover, the upper critical field H
c2 was studied by the resistivity measurements under different
magnetic fields, where an anisotropy of 8 was revealed near the superconducting
transition. Importantly, a rather steep increase for the in-plane H
c2
ab
with cooling, dμ0
H
c2
ab
/dT|
T
c
= −50.9 T/K, was observed. This value is several times higher
than that of other systems of Fe-based superconductor and indicates
an extremely high upper critical field. Possible origins for this
behavior were discussed. The finding in our work is a great promotion
both for understanding the physical properties and for the high-field
applications of 12442-type Fe-based superconductors.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.