Dilute Al-Mn alloys for superconductor device applications

We discuss results on the superconducting and electron-transport properties of Mn-doped Al produced by sputter deposition. The critical temperature of Al has been systematically reduced to below 50 mK by doping with 1000-3000 ppm Mn. Values of the α parameter are in the range of 450-500, indicating sharp normal-to-superconductor transitions. This material is thus of significant interest for both transition-edge sensors operating in the 100 mK regime and superconductor/insulator/superconductor and superconductor/insulator/normal devices, in the latter case where appropriately doped Al-Mn replaces the normal metal