Evidence for Mn clustering in dilute CuMn alloys from high-field (40 T) magnetization curves at 4.2 K

Magnetization curves of CuMn alloys with Mn concentration between 1.5 and 10 at.% have been measured at 4.2 K in fields up to 40 T, using a pulsed-field method.The results found for different concentrations can be scaled upon one another, which is a clear indication for the occurance of magnetic clusters. Analysis of this universal curve in terms of Brillouin functions yields the values $\text{z}{}_{\mathrm{I}}\text{J}{}_{\mathrm{I}}\text{/k??44K}$, $\text{z}{}_{\mathrm{II}}\text{J}{}_{\mathrm{II}}\text{/k??10K}$ and $\text{z}{}_{\mathrm{III}}\text{J}{}_{\mathrm{III}}\text{/k??0.5K}$, for the largest three interactions within each cluster.