Enhanced superconducting properties in FeCr${}_x$Se

Abstract

We report an enhancement of superconducting transition temperature ($T_{\mathrm{c}}$) when Chromium (Cr) is substituted in excess at the Iron (Fe) site (FeCr${}_x$Se, $x=$0.01, 0.02 and 0.03). There is a corresponding increase in the superconducting volume fraction with $T_{\mathrm{c}}$ attaining a value of 11.2 K on 2 Cr substitution when compared to a $T_{\mathrm{c}}$ of 8.5 K for the conventional tetragonal Fe-excess sample Fe${}_{1+x}$Se. 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.

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