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Abstract Neutron-diffraction and direct magnetic measurements have been used to determine the magnetic structures of platinum + iron alloys in the neighbourhood of the composition Pt3Fe. It is found that the magnetic structure is sensitively dependent on the precise chemical order, in particular on the number of nearest-neighbour iron atoms. Alloys of the stoichiometric composition, where the chemical order is perfect, have a simple antiferromagnetic structure, but addition of excess iron leads to the coexistence of two different structures, with different Néel temperatures but a single, undistorted, cubic unit cell. An incipient ferromagnetic state which shows a cluster type of behaviour is associated with the presence of excess iron. Increase of iron content beyond 34 % leads to the growth of bulk ferromagnetism. Throughout the sequence of structural changes the iron atoms carry a magnetic moment of about 3.3 μB and there appears to be very little alined moment on the platinum atoms.
Bacon et al. (Tue,) studied this question.