Fabrication of L10-ordered FeNi films by denitriding FeNiN(001) and FeNiN(110) films

L10-ordered FeNi (L10-FeNi) has attracted attention as a rare-earth-free material with large uniaxial magnetic anisotropy energy (Ku). In this study, FeNiN(001) and FeNiN(110) films were grown epitaxially, and fabrication of L10-FeNi(001) and L10-FeNi(110) films were attempted by denitriding these FeNiN films. FeNiN(001) films were grown epitaxially on MgAl2O4(001) substrates by alternate monoatomic layer deposition of FeN and Ni layers using molecular beam epitaxy. However, the degree of crystal orientation and Fe-Ni long-range order (S) of the L10-FeNi(001) films after denitridation were low, and Ku was small (0.08 MJ/m3). These small S and Ku values were attributed to the release of N atoms through both Fe and Ni planes during denitridation. In contrast, for the L10-FeNi(110) films prepared by denitriding the FeNiN(110) films grown epitaxially on LaAlO3(110) substrates by the co-deposition of Fe, Ni, and N, S = 0.60 and Ku = 0.55 MJ /m3. When N atoms were desorbed by passing only through the Fe plane during denitridation, relatively large values of S and Ku were obtained. Therefore, the difference in the crystal orientation of the FeNiN films strongly affected the S and Ku values of the L10-FeNi films after denitridation. Moreover, first-principles calculations suggested that the N atoms escaped via the tetrahedral interstitial sites between the Fe and Ni layers in L10-FeNi.

Automated summary

In this study, L10-FeNi(001) and L10-FeNi(110) films were successfully fabricated by denitriding FeNiN films. The crystal orientations and Fe-Ni long-range order of the FeNiN films strongly influenced the properties of the resulting L10-FeNi films. The N atoms escaped through the tetrahedral interstitial sites in the L10-FeNi structure.