Figure 1

Reduced critical temperature and low-temperature resistivity versus Mn concentration for Al-Mn alloys from resistive transitions as open circles [17], solid circles [15], and solid squares [16], and our work as solid triangles. Error bar reflects uncertainty based on RBS results. We also include our results from tunnel measurements as open triangles. Also included are results for the Kaiser and Abrikosov-Gorkov theories as solid and dashed lines, respectively. Values of low-temperature resistivity for our work are indicated by open squares. $T_{\mathrm{co}}\equiv 1.2\mathrm{K}$ and ${\rho }_o$ is the resistivity just above $T_{\mathrm{c}}$. Inset shows the resistive transitions for Al-Mn films with 1000 and 1500 ppm Mn [28].Reuse & Permissions

Figure 2

Normalized tunnel conductance versus bias for Al-Mn/oxide/Al-Mn tunnel junctions with Mn doping concentrations as indicated. All measurements made at $70<T<80\mathrm{mK}$. Data are solid symbols and solid lines are fits with the Kaiser theory for nonmagnetic impurities. Dashed lines illustrate the expected linear dependence of peak height with bias, based on the Kaiser model with constant Dynes broadening. Values of the Dynes parameter used to fit the 0, 750, 1000, and 1200 ppm data were $\Gamma =2.9$, 1.75, 3.1 and $2.9\mu \mathrm{eV}$, respectively. Inset shows the current-voltage characteristics for the junction with 1000 ppm Mn.Reuse & Permissions

Figure 3

Normalized conductance versus reduced bias for the data in Fig. 2 (solid symbols), with energy gaps $\Delta =186$, 109, 88.5, and $67.0\mu \mathrm{eV}$ for junctions with Mn concentrations of 0, 750, 1000, and 1200 ppm, respectively. Shown are fits with the Kaiser theory including Dynes broadening from Fig. 2 (here with red lines), and Kaiser theory including magnetic-impurity broadening (blue lines), with values of $2\alpha =0.8$, 0.7, 1.5, and $2.0\mu \mathrm{eV}$ for junctions with Mn concentrations of 0, 750, 1000, and 1200 ppm, respectively. The dashed lines show the Abrikosov-Gorkov result for the case of magnetic Mn impurities. Plots offset by 10 vertical units for clarity.Reuse & Permissions