dHvA observation of spin-dependent scattering by magnetic pairs of Co impurities in Au

We report the first dHvA observations of interaction effects between impurities, via measurements of the spin-dependent scattering of conduction electrons by magnetic pairs of Co impurities in Au. The local moment associated with Co pairs produces the only spin-dependent scattering in these dilute alloys because isolated Co impurities (which are also present) carry no local moment at low temperatures. The results are used to estimate the concentration (or average separation) of magnetic pairs.