Atomic clustering and magnetic defects in antiferromagnetic Cr-6.5at%Fe

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Abstract
The neutron polarisation analysis technique has been used to measure the atomic disorder and magnetic defect scattering from an antiferromagnetically commensurate Cr-6.5at%Fe alloy. The atomic disorder scattering is consistent with a model in which iron atoms cluster, each impurity iron atom having on average 1.6 further iron atoms in its first-near-neighbour shell. The magnetic defect scattering suggests that the presence of an iron impurity atom reduces the magnetic moment on chromium sites in the first- and second-neighbour shells to almost zero. Although no static moment has been observed on the iron site it is inferred from the results, in conjunction with previously reported magnetic measurements of CrFe, that the iron atoms are coupled together magnetically to form superparamagnetic assemblies which remain uncorrelated with the antiferromagnetically ordered chromium matrix.