Quasi-two-dimensional behavior of 112-type iron-based superconductors

Abstract

Fluctuation magnetoconductivity and magnetization above the superconducting transition temperature (${T}_{c}$) are measured on the recently discovered 112 family of iron-based superconductors (IBS), ${\mathrm{Ca}}_{1\ensuremath{-}x}{\mathrm{La}}_{x}{\mathrm{Fe}}_{1\ensuremath{-}y}{\mathrm{Ni}}_{y}{\mathrm{As}}_{2}$, which presents an extra As-As chain spacer-layer. The analysis in terms of a generalization of the Lawrence-Doniach approach to finite applied magnetic fields indicates that these compounds are among the most anisotropic IBS ($\ensuremath{\gamma}$ up to $\ensuremath{\sim}30$) and provides compelling evidence of a quasi-two-dimensional behavior for doping levels near the optimal one.