Rare earth permanent magnets play a key role in view of the increasing market for green energy applications and new materials which can compete with Nd2Fe14B but are environmentally less problematic are highly sought after. Fe-based ThMn12 phases contain less RE material than the commercially used compounds and have attracted quite some interest. An efficient and resource saving way to identify out of this class new phases which have the potential to become permanent magnets is by computational materials design. However, predicting the magnetic properties of 4f systems is challenging because of the localization of the 4f electrons which determines to a large extend the level of theory needed for a reliable description and prediction. We have shown that the 4f electrons in Sm 1:12 can be viewed as fully localized and can be safely treated as core electrons while for CeFe11Ti the correlation effects are smaller and the 4f states can still be viewed as valence states [1,2]. In the case of NdFe11Ti the 4f electrons are partially localized as can be seen from the hybridization function in Fig. 1. The hybridization function serves as a qualitative measure for the interaction of the 4f electrons with the valence electrons in a system [3]. As a consequence of the partial localization, the cone type magnetocrystalline anisotropy (MCA) of the latter system is only observed in a DFT+U description with an intermediate Hubbard U value, see Fig. 2. Assuming full localization (4f in core) results in a uniaxial MCA which contradicts the experimental findings at low temperatures. Plain DFT also fails. It is also discussed in how far the strong dependence of the MCA and related magnetic properties of NdFe11Ti on the theoretical description influences the prediction of new phases. As test case the quaternary system Nd1-xYxFe12-yTiy was chosen. Supported by NOVAMAG (EU686056), the Swedish Foundation for Strategic Research (EM16-0039), and SNIC (Swedish National Infrastructure for Computing).

![](https://assets.underline.io/uploads/markdown_image/1/image/4ef356ea30502b13556ecaaaa8bde227.jpg)

![](https://assets.underline.io/uploads/markdown_image/1/image/d1615ec9348ff3d8df6e838f0771e695.jpg)

New potential materials for rare earth lean permanent magnets from computational design and the challenge of the 4f electrons

New potential materials for rare earth lean permanent magnets from computational design and the challenge of the 4f electrons

Where the high-performance permanent magnets are needed (e.g. in the area of ‘green’ energy technology, such as electric vehicles and windmills) rare-earth (RE) magnetic materials dominate. At the same time, the heavier RE elements are quite expensive, some of them are rapidly decreasing in availability, and are often mined with the methods that leave an environmental footprint. Additionally, nowadays, there is a gap between the ‘strong’ RE-based magnets and their RE-free alternatives. We are using the data-mining approach in the search for high (and medium)-performance RE-free/lean magnetic materials. Filtering through a large number of known structures from ICSD database [1], we are looking for materials with high magnetization M &gt; 1 T, uniaxial MAE &gt; 1 MJ/m3, and Tc &gt;300 K. Sometimes, additional elements alterations are attempted to tweak the properties that are below the required values or make the material more cost-effective. Two searches have already been performed – a search amongst the materials containing a 3d- and a 5d-elements [3] and the materials that contain at least two 3d- metals [4]. New material was found (that had not been used as a permanent magnet before) and consequently synthesized by our experimental collaborators – Co3Mn2Ge [4]. From the ab-initio calculations, the defect-free material was predicted to have the saturation magnetization of 1.71 T, the uniaxial magnetocrystalline anisotropy of 1.44 MJ/m3, and the Curie temperature of 700 K. The samples synthesized, however, were found to have a partial disorder of Co and Ge. A saturation polarization of 0.86 T at 10 K was detected, together with a uniaxial magnetocrystalline anisotropy constant of 1.18 MJ/m3, and the TC = 359 K. These magnetic properties make Co3Mn2Ge a very promising material to be considered as a rare-earth free permanent magnet. Its magnetism depends critically on the amount of disorder of the Co and Ge atoms, a further improvement of the magnetism is possible. The next high-throughput search is being currently performed in collaboration with the experimental colleagues. We would like to acknowledge the financial support of the SSF and SNIC for the computation resources.

High-throughput and Data-mining Search for Novel Rare-Earth-Free Permanent Magnets

High-performance permanent magnets are needed for a large number of applications, especially ‘green’ energy conversion, such as electric motors and windmills, which require them in extremely large quantities. At the same time, the heavier rare-earth elements which are necessary for obtaining the good magnetic characteristics of these materials (such as Pr, Nd, Sm, Tb, or Dy), are often mined with methods that leave an environmental footprint, quite expensive, and are rapidly decreasing in availability. We are using a high-throughput and data-mining approach to the search of rare-earth free permanent magnets by filtering through a large number of known structures from ICSD database [1]. Using a full-potential linear muffin-tin orbital method with the relativistic formulation as implemented in the RSPt electron structure code [2] we calculate the magnetic moment (M), magnetic anisotropy energy (MAE), and Curie temperature, looking for the materials with high M &gt;1 T, uniaxial MAE &gt;1 MJ/m3, and Tc &gt;300 K to identify the suitable replacement for rare-earth containing materials. To test the method, we investigated the materials containing a 3d-, a 5d-, and one extra element of the periodic table and found several candidates that have characteristics suitable for a good permanent magnet (Pt2FeCu, Pt2FeNi, W2FeB2, etc). Based on this result we have also proposed two new materials, not existing in ISCD database - Pt2FeCo and Pt2CoNi [3]. The second run was performed for the materials that contain at least two 3d- metals (with no restriction on the number of elements). Based on this run, new material was found (that had not been used as a permanent magnet before) and consequently synthesized, that has the high magnetization, MAE, and Tc. Hence, a new class of rare-earth-free permanent magnets has been proposed. We would like to acknowledge the financial support of the SSF and SNIC for the computation resources.

**References:**

1. http://www2.fiz-karlsruhe.de/icsd_home.html 2. John M. Wills et al., arXiv:cond-mat/9912173 (1999) 3. A. Vishina, O. Yu. Vekilova, T. Björkman, A. Bergman, H. C. Herper and O. Eriksson Phys. Rev. B 101, 094407 (2020)

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 High-throughput and Data-mining Search for Rare-earth-free Permanent Magnets

**Session chair:** Hossein Sepehri-Amin, National Institute for Materials Science


DOA - Rare-earth Hard Magnetic Materials

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New potential materials for rare earth lean permanent magnets from computational design and the challenge of the 4f electrons

High-throughput and Data-mining Search for Novel Rare-Earth-Free Permanent Magnets

High-throughput and Data-mining Search for Rare-earth-free Permanent Magnets

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