title: Computational design of magnetic materials for energy applications
Creators: name: Santos Fortunato, Nuno Miguel dos
Publisher: name: UNSPECIFIED
Year: 2025

description: At present there is a growing demand for refrigeration and cooling applications, with an expected commensurate increase in energy consumption. In this sense, functional magnetic materials enable numerous technologically relevant applications, such as magnetic cooling, energy conversion and energy harvesting. By exploiting the magnetocaloric effect, magnetic refrigeration promises to be an efficient and environmentally friendly cooling technology, however, it requires materials with a slew of optimized magnetic and structural properties, such as a large adiabatic temperature change and good mechanical behaviour. On the other hand, magnetic materials can exhibit emergent transport properties, e.g., the anomalous Hall and Nernst effects, with the latter allowing for the realisation of transverse thermoelectric devices. Such transport effects can be attributed to the presence of topological band structure features that contribute to the Berry curvature, e.g Weyl points and nodal lines, with their distance to the Fermi energy being a key factor and subject to optimization.

High-throughput screenings based on density functional theory calculations have been used as a method to accelerate materials discovery, with the aim of screening for stable compounds with intriguing properties. However, the application of such studies to magnetocaloric materials is still lacking, with no overreaching design strategy to tackle first-order magnetic transitions. In this work, a high-throughput procedure was implemented and applied to two classes of intermetallic systems - MM'X alloys (M &amp; M'=metals, X=main-group) and all-d-metal Heusler compounds, in order to screen for promising candidates for caloric applications. We identified trends in key features of these systems, such as stability and relative bonding strengths in MM'X alloys. While in the all-d-metal Heusler family, we discussed how d-d bonding affects the mechanical behaviour and structural preference in this material class. In order to tackle the critical aspect of the magnetocaloric behaviour, we implement a computational workflow that screens for the magnetic and structural states that enable a first-order transition and then describes the finite-temperature effects that drive it. Using the notion of the Curie temperature window within an ab initio framework, we inform the selection and optimization of MM'X and all-d-metal Heusler compounds with potential magneto-structural transitions. We further predict how such properties can be controlled through isostructural substitution, guided by the results of our high-throughput study. We further explored the anomalous Hall and Nernst effects in the all-d-metal Heusler systems that were labelled as stable, and discussed the dependence of such effects on electron filling.

The results presented here serve to enrich automated ab initio workflows, representing a systematic methodology for evaluating the thermodynamic properties of magnetic materials, while the generated databases of MM'X and all-d-metal Heusler compounds provide a possible starting point for future machine learning studies. Thus, this work opens up new possibilities for the discovery and design of functional magnetic materials.