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arXiv · 2101.10773

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

Alena Vishina·Daniel Hedlund·Vitalii Shtender·Erna K. Delczeg-Czirjak·Simon R. Larsen·Olga Yu. Vekilova·Shuo Huang·Levente Vitos·Peter Svedlindh·Martin Sahlberg·Olle Eriksson·Heike C. Herper
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Abstract

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 $T_{\rm C}$ = 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. From the theoretical works, a substitution of Ge by neighboring elements suggest two other promising materials - Co$_3$Mn$_2$Al and Co$_3$Mn$_2$Ga. 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.

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Alena Vishina, Daniel Hedlund, Vitalii Shtender, Erna K. Delczeg-Czirjak, Simon R. Larsen, Olga Yu. Vekilova, Shuo Huang, Levente Vitos, Peter Svedlindh, Martin Sahlberg, Olle Eriksson, Heike C. Herper. 2021-01-26. Data-driven design of a new class of rare-earth free permanent magnets. https://doi.org/10.1016/j.actamat.2021.116913

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