Sputtered films of superconductingSmRh4B4

Films of the coexistent antiferromagnetic superconductor ${\mathrm{SmRh}}_4$ ${\mathrm{B}}_4$ have been made by sputtering. These films have been characterized by x-rays and superconducting critical temperatures $T_c$, fields, and currents. Our best films have residual resistance ratios, $r_R$, as high as or higher than for films of ${\mathrm{ErRh}}_4$ ${\mathrm{B}}_4$ reported in the literature, and the highest $T_c$ is 2.36 K. We find an anomalous dependence of $T_c$ on $r_R$, and offer two possible explanations (proximity-effect and disorder-enhanced spin-flip scattering), as well as propose a radiation-damage experiment to distinguish between these. The antiferromagnetic ordering temperature is shown to decrease with film disorder as does the ferromagnetic ordering temperature in radiation-damaged ${\mathrm{ErRh}}_4$ ${\mathrm{B}}_4$. We find an approximately 1000-Å-thick RhAl impurity phase at the sapphire-substrate/film interface which seems to result from a reaction with the substrate. The potential importance of RhAl and trace impurity phases on present measurements and planned tunneling experiments are discussed in detail. Finally, the full critical-field curves are presented along with an explanation of why the low-temperature values are independent of $T_c$.