Data-driven design of a new class of rare-earth free permanent magnets

A new class of rare-earth-free permanent magnets is proposed. The parent compound of this class is Co 3 Mn 2 Ge, and its discovery is the result of first principles theory combined with experimental synthesis and characterisation. The theory is based on a high-throughput/data-mining search among materials listed in the ICSD database. From ab-initio theory of the defect free material it is predicted that the saturation magnetization is 1.71 T, the uniaxial magnetocrystalline anisotropy is 1.44 MJ/m 3 , and the Curie temperature is 700 K. Co 3 Mn 2 Ge samples were then synthesized and characterised with respect to structure and magnetism. The crystal structure was found to be the MgZn 2 -type, with partial disorder of Co and Ge on the crystallographic lattice sites. From magnetization measurements a saturation polarization of 0.86 T at 10 K was detected, together with a uniaxial magnetocrystalline anisotropy constant of 1.18 MJ/m 3 , and the Curie temperature of T C = 359 K. These magnetic properties make Co 3 Mn 2 Ge a very promising material as a rare-earth free permanent magnet, and since we can demonstrate that magnetism depends critically on the amount of disorder of the Co and Ge atoms, a further improvement of the magnetism is possible. We demonstrate here that the class of compounds based on T 3 Mn 2 X (T = Co or alloys between Fe and Ni; X = Ge, Al or Ga) in the MgZn 2 structure type, form a new class of rare-earth free permanent magnets with very promising performance. (c) 2021 The Author(s). Published by Elsevier Ltd on behalf of Acta Materialia Inc. This is an open access article under the CC BY license ( http://creativecommons.org/licenses/by/4.0/ )