Enhanced superconducting properties in FeCrxSe

We report an enhancement of the superconducting transition temperature (Tc) when chromium (Cr) is substituted in excess at the iron (Fe) site (FeCrxSe, x=0.01x=0.01, 0.02 and 0.03). There is a corresponding increase in the superconducting volume fraction with Tc attaining a value of 11.2 K on 2% Cr substitution when compared to a Tc of 8.5 K for the conventional tetragonal Fe-excess sample Fe1+xSe. The results point to the role of chemical pressure (introduced via ionic size variation at the Fe site upon Cr substitution in excess) on superconducting properties.

Research highlights
► Chromium (Cr) was substituted in excess at the Fe site in FeSe to obtain tetragonal FeCrxSe (x=0.01x=0.01, 0.02, and 0.03) with P4/nmmP4/nmm space group.
► With just 2% Cr excess, there is an enhancement of superconducting transition temperature Tc by about 40%.
► Could provide a route to enhance the Tc in Fe-based superconductors via suitable chemical substitutions.