Optimising the outcome of the high-throughput search for rare-earth-free permanent magnets

With the exponential growth in the number of electric vehicles and windmills required for the transition to green energy, there is an ever-increasing demand for permanent magnets (PM). However, all the materials used in these applications nowadays contain rare-earth (RE) elements, which are expensive and mined with techniques damaging for the environment.

In recent years, high-throughput and data-mining approaches have been used for various applications and have become more and more feasible. In the search for RE-free PM, we are sifting through the materials of the ICSD database [1] in the search for materials with high magnetization M > 1 T, uniaxial magnetic anisotropy energy > 1 MJ/m³, and T_C >400 K [2,3].

Several investigations were performed [2,3]. Among others, new material has been found (that had not been used as a permanent magnet before) and consequently synthesized by our experimental collaborators – Co₃Mn₂Ge [3]. From the ab-initio calculations, the defect-free material was predicted to have a saturation magnetization of 1.71 T, a uniaxial magnetocrystalline anisotropy of 1.44 MJ/m³, and a Curie temperature of 700 K.

To improve on the results of the search among the materials with a 3d and a p-block element, an additional study was performed. For example, a structure of Mn₂(X_0.5Y_0.5)B₄ (X,Y = Mo, W, Ta, Cr) form was considered as a combination of two promising materials - Mn₂WB₄ and Mn₂MoB₄ to improve the Curie temperature [4]. Doping of Fe₂C was investigated to increase the structure’s stability [4].