Single Crystal Growth of Cuprate Superconductor (Lu${}_{0.8}$Nd${}_{0.2}$)Ba${}_2$Cu${}_4$O${}_8$ by KOH Flux Method

Single crystals of Nd-substituted LuBa${}_2$Cu${}_4$O${}_8$ were successfully grown by the KOH flux method. The single phase of Lu${}_{1-x}$Nd${}_x$Ba${}_2$Cu${}_4$O${}_8$ [(Lu,Nd)124] formed at $x=0.2$. The compound crystallized as orthorhombic Ammm structure with lattice constants of a = 3.835(3) {\AA}, b = 3.879(2) {\AA} and c = 27.195(6) {\AA}. Single crystal structural analysis demonstrated that the Nd ion partially occupied the Lu site. The (Lu,Nd)124 exhibited the superconducting transition at ~75 K in the magnetic susceptibility and resistivity. The $T_c$ and the c-axis of the (Lu,Nd)124 corresponded to Tm124. These results indicate that RE124 equivalent to the one composed of single RE element is obtained by combination of two RE elements.