Effect of axial ratio and atomic volume on magnetism of α′ and γ′-Fe-N

α′ (bct) and γ′(fct)-Fe-N with various N contents and unit-cell volumes were synthesized by using a multilayer fabrication technique. The effect of axial ratio and atomic volume on magnetism of these phases was examined. The atomic volume of α′ and γ′ phases monotonously increases with increasing either N content of Fe-N layers or in-plane lattice spacing of intermediate layers. In both cases of α′ and γ′-Fe-N, the magnetic moment increases with increasing atomic volume. This result qualitatively corresponds to theoretical prediction. In the case of α′-Fe-N, the magnetic moment increases with an increasing axial ratio. On the other hand, in the case of γ′-Fe-N, the magnetic moment decreases with an increasing axial ratio. In the case of α′-Fe-N, the exchange integral (J) does not change against both atomic volume and axial ratio. On the other hand, in the case of γ′-Fe-N, J increases with increasing atomic volume and slightly decreases with increasing axial ratio. Judging from these results, we can expect to further enhance the magnetic moment with relatively high T _c, when we could realize the intermediate state of α′ and γ′-Fe-N.