Effect of RKKY interactions on the magnetization of dilute magnetic alloys with hcp hosts

The magnetization due to the presence of magnetic impurities dissolved dilutely in nonmagnetic H.C.P. host metals has been calculated assuming a fine structure splitting by an axially symmetric crystal field and an RKKY interaction between the impurities. To compute the RKKY contribution, the interaction between the impurities is described by a randomly oriented effective internal exchange field H with a probability distribution P(H) = ∆ /ir2(∆ 2 + H2)2 . Comparison of the calculated magnetization with the measured magnetization of a 5 ppm single crystal of MgMn and several polycrystalline ZnMn samples of varying concentration, over the temperature range 2K to 10mK, yields estimates for ∆, the most probable value of the magnitude of the effective exchange field, as well as the dependence of ∆ on impurity concentration.