Iron nitrides: High-pressure synthesis, nitrogen disordering and local magnetic moment

Abstract Iron nitride (Fe x N y ) is a promising candidate for the next generation of ferromagnetic materials. However, synthesizing high-quality bulk iron nitride with tuned structure and magnetic properties remains a challenge. Currently, experimental and theoretical results regarding the magnetic property of iron nitrides remain controversial. With the recent advancements in high-pressure technology, new synthetic pathways to iron nitrides have been proposed. High-pressure synthesis technology provides multidimensional possibilities for tuning the structure and magnetic properties of iron nitrides. This review summarizes recent progress in high-pressure synthesis of iron nitrides, especially the high-pressure solid-state metathesis reaction synthesis (HSM). We have summarized the reaction characteristics of HSM. The HSM reaction exhibits vector synthesis characteristics and promotes nitrogen disorder diffusion at high temperature. Due to this, the HSM reaction can achieve the synthesis of multinary iron-based metal nitrides and regulate the local magnetic moments. It serves as a powerful means for tuning the structure and magnetic properties of iron nitrides. Taking advantage of neutron diffraction in characterizing local magnetic moment and nitrogen disorder in iron nitrides, the relationship between iron local magnetic moment and nitrogen content has been elucidated. Moreover, the development of high-pressure in-situ imaging technology based on large-volume press allows the real-time observation of HSM reaction process. In this review, we also report our latest experiments on neutron diffraction and high-pressure in-situ image for the study of iron nitrides.