Local ordering and magnetism in Ga0.9Fe3.1N

Abstract Prior investigations of the ternary nitride series Ga 1– x Fe 3+ x N (0≤ x ≤1) have indicated a transition from ferromagnetic γ ′-Fe 4 N to antiferromagnetic “GaFe 3 N”. The ternary nitride “GaFe 3 N” has been magnetically and spectroscopically reinvestigated in order to explore the weakening of the ferromagnetic interactions through the gradual incorporation of gallium into γ ′-Fe 4 N. A hysteretic loop at RT reveals the presence of a minority phase of only 0.1–0.2 at%, in accord with the sound two-step synthesis. The composition of the gallium-richest phase “GaFe 3 N” was clarified by Prompt Gamma-ray Activation Analysis and leads to the berthollide formula Ga 0.91(1) Fe 3.09(10) N 1.05(7) . Magnetic measurements indicate a transition around 8 K, further supported by Mossbauer spectral data. The weakening of the ferromagnetic coupling through an increasing gallium concentration is explained by a simple Stoner argument. In Ga 0.9 Fe 3.1 N, the presence of iron on the gallium site affects the magnetism by the formation of 13-atom iron clusters.