Classification of magnetic structures in compounds with the Fe₂P-structure

A study is made of possible spin configurations in Fe₂P permitted by the symmetry considerations provided that the magnetic and crystallographic cells coincide. In the exchange approximation a number of magnetic structures is revealed. It is found that alongside with the standard ordering types: ferromagnetic (FM), ferrimagnetic (FIM), antiferromagnetic with the triangular spin lattice (AFM), there are non-trivial structures: antiferromagnetic-paramagnetic (AFM-PM) and antiferromagnetic-ferrimagnetic (AFM-FIM). The account of relativistic interactions leads to the upset of collinearity between the sublattice magnetic moments in the FM and FIM structures of the "easy-plane" type and in the basal plane of the AFM-FIM and AFM-PM structures. In the latter case a moment on the paramagnetic ion appears. These processes result in the change of the net moment and appearance of the weak ferromagnetic moment in the AFM-FIM and AFM-PM as well as in some AFM structures.