Magnetic Correlations In Gamma-Mn And A Mn-10 At%Cu Alloy

We have carried out first-principles calculations of the paramagnetic susceptibilities of gamma-Mn and a Mn-10 at%Cu solid solution in which the paramagnetic state is modelled in terms of fluctuating 'local moments'. We find that both systems exhibit clear antiferromagnetic correlations. These an significantly stronger in the alloy. We show that this is caused by Cu impurity states reducing the dispersion of some Mn d-states. This increases the magnitude of the Mn local moments which interact antiferromagnetically. The Neel temperature of the gamma-Mn is found to be 267 K, whereas that of Mn-10 at%Cu is 382 K. (C) 1998 Elsevier Science B.V. All rights reserved.