L1 ₀ FeNi: a promising material for next generation permanent magnets

Permanent magnets (PM) find widespread application in energy conversion, telecommunication, data storage, sensors, electronic gadgets, etc. Even though the market for PM is dominated by rare earth (RE) based magnets like Nd-Fe-B and Sm-Co, the recent crisis of RE elements and supply constraints have evoked the necessity of new PM materials for sustainable development. Owing to the predicted high value of (BH)max, the abundant availability of constituent elements (Fe, Ni), and presence in natural meteorites, L10 FeNi has drawn the attraction of the scientific community. Therefore, in this article, L10 FeNi (tetrataenite) is extensively reviewed as one of the most suitable candidates for future permanent magnetic material. Although L10 FeNi has shown immense potential for PM application due to its high magnetocrystalline anisotropy and magnetic saturation, the bulk synthesis of this material is not yet achieved. The problems in laboratory synthesis of L10 FeNi and the technological limitations for practical use are dominated by the slow diffusion of Ni in the FeNi lattice around the low order-disorder temperature (∼593 K). Artificial techniques with a low-temperature synthesis of ordered L10 FeNi are highlighted and the properties of L10 FeNi thin films are also presented coherently.