Synthesis of <i>L</i>1₂-FeNi Nanoparticles by Nitrogen Insertion and Topotactic Extraction Method

Abstract

The nitrogen insertion and topotactic extraction (NITE) method was used to explore an unknown metastable phase of an FeNi alloy with an Fe:Ni ratio of 1:1. We found that partly ordered non-equilibrium L12-FeNi can be obtained through Fe2Ni2N as the intermediate nitride phase. The experimental results of both x-ray diffraction and transmission electron microscopy with energy dispersive x-ray spectrometry are consistent in identifying the denitrided material as L12-FeNi. Ni atoms preferentially occupy the corner sites in an estimated 96% of cases. No significant difference was found in the magnetization curves between the precursor of A1-FeNi and L12-FeNi particles. Our results suggest that the NITE method is not only a useful way for synthesizing fully ordered alloys of equilibrium phases such as L10-FeNi but also for creating metastable phases like L12-FeNi.

Epitaxial L1-FeNi films with high degree of order and large uniaxial magnetic anisotropy fabricated by denitriding FeNiN films

“…On the other hand, we synthesized L1 0 -FeNi powder with an S of 0.71 by extracting nitrogen atoms from antiferromagnetic tetragonal FeNiN powder, 17 where FeN and Ni monoatomic layers are alternately stacked in the c-axis direction due to the higher affinity of Fe-N bonds than that of Ni-N bonds, [18][19][20][21][22] by the annealing in a H 2 gas atmosphere while maintaining the Fe/Ni ordered structure. A coercivity of 142 kA/ m was achieved in the L1 0 -FeNi powder but its K u value was not evaluated because of its polycrystalline form.…”