Magnetic Properties of Iron Nitride Thin Films

Iron nitride thin films encompass a rich variety of crystallographic phases, notably γ′-Fe₄N, ε-Fe₃N, and α″-Fe₁₆N₂, each distinguished by unique magnetic characteristics. Control of nitrogen concentration and deposition parameters governs phase formation, enabling tuning of saturation magnetisation, coercivity and magnetocrystalline anisotropy. Epitaxial strain, induced by choice of substrate or seed layer, further modulates magnetic ordering and anisotropy, while ion‐implantation and post‐annealing routes permit synthesis of free‐standing foils with high energy products. Monolayer iron nitride islands on metallic substrates reveal surface‐confined phases with altered work function and spin polarisation, which are of direct relevance to spintronic interfaces. The high saturation magnetisation of α″-Fe₁₆N₂, combined with its rare‐earth‐free composition, positions iron nitride films as promising candidates for permanent magnets, high‐density recording media and spin‐injection layers in semiconductor heterostructures. Challenges remain in stabilising single‐phase films, controlling grain size and sustaining thermal stability under operating conditions.

Research from Nature Portfolio

Recent studies have proposed simultaneous enhancement of magnetic anisotropy and thermal stability in α″-Fe₁₆N₂ by deliberate substitution of Fe with higher‐valence elements. Computational analysis suggests that Co, Ni, Ga or Al doping can elevate uniaxial magnetocrystalline anisotropy energy up to 2.4 MJ m⁻³, three times that of the undoped phase, while improving phase stability without recourse to heavy or rare‐earth elements. First‐principles investigations of exchange interactions in pure and V‐doped Fe₁₆N₂ reveal the underlying mechanism for its giant magnetic moment and predict Curie temperatures approaching or exceeding experimental observations, alongside high spin polarisation suitable for injecting spins into III–V semiconductors. Seminal experimental work demonstrated synthesis of free‐standing α″-Fe₁₆N₂ foils via nitrogen ion implantation and two‐step annealing, achieving coercivity values up to 1910 Oe and magnetic energy products of 20 MGOe, thereby offering a scalable route to rare‐earth‐free permanent magnets.

Magnetic Properties of Iron Nitride Thin Films publication trend

The graph below shows the total number of articles in magnetic properties of iron nitride thin films across all publications each year (not limited to Nature Index journals).

Technical terms

α″-Fe₁₆N₂: An iron‐rich nitride phase exhibiting exceptionally high saturation magnetisation and large magnetocrystalline anisotropy.

Magnetocrystalline anisotropy: The dependence of a material’s magnetic energy on the direction of magnetisation relative to its crystal lattice.

Coercivity: The magnetic field strength required to reduce the magnetisation of a material to zero after saturation.

Saturation magnetisation: The maximum magnetisation a material can attain under an external magnetic field.

Spin injection: The transfer of spin‐polarised electrons from a ferromagnetic material into a non‐magnetic semiconductor.

Rigid‐band analysis: A computational approach that models the effect of electron doping on electronic structure by shifting the Fermi level without changing the underlying band structure.

Epitaxial strain: Lattice distortion in a thin film induced by mismatch with the substrate, influencing electronic and magnetic properties.

References

1. Iron Nitride Thin Films: Growth, Structure, and Properties. Crystal Growth & Design (2022).
2. Synthesis of Fe16N2 compound Free-Standing Foils with 20 MGOe Magnetic Energy Product by Nitrogen Ion-Implantation. Scientific Reports (2016).
3. Structure of monolayer iron nitride islands on Cu(001) revisited. Vacuum (2024).
4. Simultaneous tuning of the magnetic anisotropy and thermal stability of α′′-phase Fe16N2. Scientific Reports (2021).
5. Engineering perpendicular magnetic anisotropy in Fe via interstitial nitrogenation: N choose K. APL Materials (2016).