Database of novel magnetic materials for high-performance permanent magnet development

Abstract

This paper describes the open Novamag database that has been developed for the design of novel Rare-Earth free/lean permanent magnets. The database software technologies, its friendly graphical user interface, advanced search tools and available data are explained in detail. Following the philosophy and standards of Materials Genome Initiative, it contains significant results of novel magnetic phases with high magnetocrystalline anisotropy obtained by three computational high-throughput screening approaches based on a crystal structure prediction method using an Adaptive Genetic Algorithm, tetragonally distortion of cubic phases and tuning known phases by doping. Additionally, it also includes theoretical and experimental data about fundamental magnetic material properties such as magnetic moments, magnetocrystalline anisotropy energy, exchange parameters, Curie temperature, domain wall width, exchange stiffness, coercivity and maximum energy product, that can be used in the study and design of new promising high-performance Rare-Earth free/lean permanent magnets. The results therein contained might provide some insights into the ongoing debate about the theoretical performance limits beyond Rare-Earth based magnets. Finally, some general strategies are discussed to design possible experimental routes for exploring most promising theoretical novel materials found in the database. NOVAMAG H c > M r /2 [5]. Extrinsic properties also depend on temperature, in fact they typically decrease as temperature increases, reducing the magnet's performance, especially close to the Curie temperature T C (i.e. ferromagnetic-paramagenetic transition). The macroscopic behavior is tightly linked to the microscopic properties called intrinsic. Main magnetic intrinsic properties are atomic magnetic moment µ at (the magnetic moment per volume gives the maximum theoretical M s ), exchange interactions J ij (which determine the magnetic order and T C )and magnetocrystalline anisotropy K 1 (that can enhance H c and it is indispensable in modern magnets to get H c > M r /2) [6]. PMs should have high atomic mangetic moments per volume (> 0.1µ B /Å 3 ), strong ferromangetic exchange interactions (able to give T C > 600 K) and high easy axis magnetocrystalline anisotropy (K 1 > 1 MJ/m 3 ) in order to exhibit good extrinsic properties suitable for PM applcations. In particular, magnetic materials with hardness parameter κ = K 1 /(µ 0 M 2 s ) > 1 (called "hard" magnets) are very valuable since can be used to make efficient magnets of any shape [6]. At mesoscopic scale, intergranular structure between the grains and crystallographic defects can strongly affect the performance of a magnet [7]. Therefore, the optimization of the material's microstructure is also very important in the design and devel-

Machine learning assisted hierarchical filtering: a strategy for designing magnets with large moment and anisotropy energy

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Interstitial Atom Engineering in Magnetic Materials

“…In past years, domain control of ferromagnets has been studied [1]. Since the 1980s, interstitial atoms have attracted intense attention related to the improvement of magnetic properties of rare-earth Fe and Co-based permanent magnets [2][3][4][5][6].…”

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