Superconducting state in (Eu1-x Ca x )RbFe4As4 with 1144-type Structure

We report the Ca substitution effect of the Fe-based superconductor EuRbFe₄As₄ with 1144-type structure (crystal system: tetragonal, space group: P4/mmm (No. 123)), in order to elucidate the relationship between the superconductivity and the magnetic order. The lattice constant systematically changed with the Ca concentration x. By Ca-substitution, the magnetic order is suppressed, while T _c is almost unchanged. The results indicate that the superconductivity of EuRbFe₄As₄ is not sensitive to the magnetic order.