Magnetic Properties of Permanent Magnet Alloys

Permanent magnet alloys are indispensable in modern technology, underpinning applications from electric vehicle motors to wind turbines and consumer electronics. Their performance is chiefly characterised by coercivity (resistance to demagnetisation), remanence (residual magnetisation after removal of an external field) and maximum energy product (a measure of stored magnetic energy). These properties emerge from a complex interplay of intrinsic factors—such as magnetocrystalline anisotropy and saturation magnetisation—and extrinsic factors, notably microstructure, phase distribution and grain boundary chemistry. Alloy composition, including the choice and proportion of rare‐earth elements or alternative transition metals, dictates the crystallographic phases present and thus the magnet’s anisotropy and thermal stability. Advances in processing techniques, from powder bed fusion to diffusion treatments, enable precise control of grain size, texture and intergranular phases, which in turn optimise coercivity by impeding domain wall motion. Balancing high performance with critical‐material supply risks has driven research into both rare‐earth‐rich and rare‐earth‐reduced systems, aiming to sustain coercivity at elevated temperatures while mitigating reliance on scarce elements.

Research from Nature Portfolio

Innovative additive manufacturing approaches have demonstrated the feasibility of near‐net‐shape production for bonded NdFeB magnets, achieving coercivity and energy products comparable to injection‐moulded counterparts by optimising polymer–powder composites and processing parameters. Inhomogeneous distribution of abundant rare‐earth elements within the 2:14:1 phase has been shown to enhance exchange coupling and magnetostatic interactions, leading to high figure‐of‐merit permanent magnets with reduced reliance on critical heavy rare earths. Detailed atomic‐scale investigation of samarium‐cobalt based alloys has revealed how precise control of cellular nanostructure and dopant content governs domain‐wall pinning strength, directly correlating microscopic phase architecture with macroscopic coercivity and thermal stability in high‐temperature applications.

Magnetic Properties of Permanent Magnet Alloys publication trend

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

Technical terms

Coercivity: The intensity of reverse magnetic field required to reduce magnetisation to zero. Remanence: The residual magnetic flux density retained in a magnet after external magnetising field is removed. Maximum energy product (BHmax): A measure of the maximum magnetic energy density a magnet can deliver. Magnetocrystalline anisotropy: The directional dependence of a material’s magnetic properties arising from its crystal lattice. Microstructure: The arrangement and size of grains, phases and interfaces within an alloy that influence magnetic behaviour. Exchange coupling: The interaction between adjacent magnetic domains or phases that affects overall magnetic performance.

References

1. Toward understanding the microstructure characteristics, phase selection and magnetic properties of laser additive manufactured Nd-Fe-B permanent magnets. International Journal of Extreme Manufacturing (2023).
2. Big Area Additive Manufacturing of High Performance Bonded NdFeB Magnets. Scientific Reports (2016).
3. Chemically Inhomogeneous RE-Fe-B Permanent Magnets with High Figure of Merit: Solution to Global Rare Earth Criticality. Scientific Reports (2016).
4. Atomic structure and domain wall pinning in samarium-cobalt-based permanent magnets. Nature Communications (2017).
5. Tomography-based digital twin of Nd-Fe-B permanent magnets. npj Computational Materials (2024).
6. High-coercivity copper-rich Nd-Fe-B magnets by powder bed fusion using laser beam method. Additive Manufacturing (2023).