Transitions from Ferromagnetism to Antiferromagnetism in Iron-Aluminum Alloys. Theoretical Interpretation

Complicated magnetic properties of $\alpha$-phase iron-aluminum alloys are successfully described from a theory with a few simple assumptions concerning the magnetic interaction between iron atoms. Two interactions are considered: the direct exchange interaction between nearest neighboring iron atoms and the indirect superexchange interaction between iron atoms separated by an aluminum atom. The model also leads to a reinterpretation of the neutron diffraction data. In view of the success of this model, it is to be concluded that the direct exchange interaction between nearest neighbor iron atoms is mainly responsible for the ferromagnetism of $\alpha$-iron.