Not too long ago, we published a two-step ammonolysis reaction which combines a high-temperature sintering step and a low-temperature nitriding reaction to yield a number of ternary magnetic nitrides of the general formula MFe3N. In the course of these investigations, we came across much older studies in which Al-substituted derivatives of γ'-Fe4N had already been mentioned. Indeed, the use of the two-step ammonolysis reaction then made us claim the existence of the compound AlFe3N in this very journal. According to our report, ferromagnetic AlFe3N was synthesized in almost phase-pure form, and the Rietveld refinement of AlFe3N based on Cu Kα_1 radiation (λ = 1.54056 A) resulted in a lattice parameter of a - 3.7967(3) A with a statistical occupation of Fe and Al (ratio 3:1) in space group Fm3m. At T = 546(20) °C both XRPD and magnetic measurements indicated the decomposition of AlFe3N into an iron—aluminum alloy. SQUID magnetometry further showed its specific saturation magnetization to be 144(2) A m~2 kg~(-1) at 5 T, about 30 smaller than for γ'-Fe4N, and the coercive field of AlFe3N was given as ten times smaller than for γ'-Fe4N. Together with the 0.25(2) T large magnetic remanence of AlFe3N, we classified the material to be a soft ferromagnet.
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