Magnetic Properties of L10-Ordered Alloys

The L10 crystal structure, exemplified by the equiatomic FeNi system known as tetrataenite, exhibits a highly ordered tetragonal lattice that underpins exceptional magnetic performance. Atomic ordering along the c-axis generates a pronounced uniaxial magnetocrystalline anisotropy, which in turn gives rise to high coercive fields and energy products suitable for permanent magnets. Unlike conventional cubic alloys, the tetragonal distortion and long-range order introduce orbital moment contributions that stabilise magnetisation against reversal. The low transition temperature for order–disorder transformation (around 593 K in FeNi) has historically limited bulk synthesis, necessitating novel non-equilibrium processing and alloy design strategies. Recent advances have addressed these challenges by exploiting pressure, alloying and templated synthesis to tune ordering kinetics and thermal stability. The promise of rare-earth-free hard magnets based on L10 phases aligns with global imperatives for sustainable energy technologies and electromobility, rendering this class of materials a focal point for both fundamental and applied research.

Research from Nature Portfolio

Recent studies have explored routes to stabilise and enhance L10 ordering through compositional and process controls. One body of work employed density functional theory to demonstrate that minor additions of elements such as Al, Ti, Cr and Co elevate the order–disorder transition temperature without significantly compromising magnetic moment or Curie temperature. Alloying thus emerges as a viable design strategy to facilitate L10 phase formation under milder conditions. Investigations into pressure effects have revealed that a modest expansion of the FeNi lattice promotes ordering, effectively lowering the barrier to tetragonal phase formation. These insights map the relationship between volume change and ordering temperature, offering a thermodynamic guide for synthesis. Complementary experimental innovation has introduced a nitrogen insertion and extraction cycle that yields single-phase L10-FeNi powder with high order parameter and a tenfold increase in coercivity, marking a significant advance in non-equilibrium synthesis of ordered alloys.

Magnetic Properties of L10-Ordered Alloys publication trend

The graph below shows the total number of articles in magnetic properties of l10-ordered alloys across all publications each year (not limited to Nature Index journals).

Technical terms

Magnetocrystalline anisotropy: The directional dependence of a material’s internal energy on the orientation of its magnetisation relative to the crystal lattice, critical for coercivity and energy product.

Long-range order parameter: A measure of atomic site occupancy regularity in an ordered alloy, ranging from zero (disordered) to one (fully ordered).

Coercivity: The magnetic field strength required to reduce the magnetisation of a material to zero, indicative of resistance to demagnetisation.

Curie temperature: The critical temperature above which a ferromagnetic material loses its spontaneous magnetisation and becomes paramagnetic.

Tetrataenite: The naturally occurring L10-ordered FeNi phase found in meteorites, serving as a model rare-earth-free hard magnet.

References

1. Alloying effect on the order–disorder transformation in tetragonal FeNi. Scientific Reports (2021).
2. Pressure effect on the order–disorder transformation in L10 FeNi. Scientific Reports (2020).
3. Synthesis of single-phase L10-FeNi magnet powder by nitrogen insertion and topotactic extraction. Scientific Reports (2017).
4. Integrated ab initio modelling of atomic ordering and magnetic anisotropy for design of FeNi-based magnets. npj Computational Materials (2024).
5. Direct Formation of Hard‐Magnetic Tetrataenite in Bulk Alloy Castings. Advanced Science (2022).
6. Revisiting Néel 60 years on: The magnetic anisotropy of L10 FeNi (tetrataenite). Journal of Applied Physics (2023).