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Research Led By Physicists At Georgetown University Demonstrates That High-Entropy Borides With Abundant Transition Metals And Boron Can Achieve High Magnetic Anisotropy Without Rare Earth Elements, Opening The Way For More Sustainable Permanent Magnets With Direct Impact On Clean Energy, Electronics, And Data Storage
Researchers at Georgetown University have identified a new class of powerful magnets free of rare earth and precious metals, based on high-entropy borides with abundant transition metals, a breakthrough that could reduce costs, environmental impacts, and geopolitical risks in modern magnetic technologies.
Fundamentals Of Anisotropy And Limitations Of Current Materials
An essential characteristic of modern magnets is magnetic anisotropy, defined as the strong preference of magnetization for a specific direction. This property underpins the performance of permanent magnets and recording media, influencing stability, efficiency, and information density.
Currently, the materials with the highest anisotropy heavily depend on rare earth elements. These elements are costly, associated with environmental impacts during extraction, and subject to supply disruptions and geopolitical instability, which affects critical industrial supply chains.
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For thin film applications, iron and platinum alloys have become benchmarks for the next generation of magnetic recording. However, the presence of the precious metal platinum poses the cost and sustainability challenge, reinforcing the need for alternatives based on abundant elements.
Finding high-performance materials that dispense with rare earth and precious metals has therefore been a long-standing scientific and technological challenge, especially for applications requiring high anisotropy and directional control of magnetization.
Discovery Of High-Entropy Borides And Design Strategy
The team led by Professors Kai Liu and Gen Yin, with participation from graduate student Willie Beeson (G’25), discovered a new type of powerful magnets based on high-entropy borides, using abundant transition metals from the Earth and boron.
These materials are free of rare earth and precious metals and establish a promising strategy for the sustainable design of magnets. The results were published in the journal Advanced Materials.
According to Liu, the approach offers a sustainable route for the manufacturing of powerful magnets applicable from future magnetic recording media to permanent magnets, while also pointing towards reducing dependence on critical materials.
High-entropy alloys contain five or more elements in nearly equal proportions and have emerged as a powerful platform for materials discovery. Their broad compositional space allows access to new structures and relevant electronic properties.
Overcoming Structural Limitations And Selection Of Phase C16
Most studies on high-entropy alloys focus on chemically disordered cubic structures, unsuitable for strong magnetic anisotropy, which favors lower crystal symmetry. This limitation has restricted the advancement of magnetism in these systems.
The researchers circumvented the issue by focusing on high-entropy borides, in which boron promotes chemical ordering and lower symmetry crystal structures. The team specifically sought a tetragonal structure known as phase C16.
Phase C16 can be envisioned as a cube elongated along one of its faces. Although known in boron-based materials with two or three elements, this structure remains underexplored in more complex and multi-component materials.
By directing the synthesis towards this symmetry, the researchers created the necessary conditions to increase magnetic anisotropy, aligning the magnetization more pronouncedly along a preferred direction.
Combinatorial Synthesis And Rapid Exploration Of Compositions
Beeson synthesized the high-entropy borides through combinatorial sputtering in Liu’s laboratory. In this method, atoms from multiple target materials are fully mixed as they are collected on a heated substrate.
The approach allowed for the rapid exploration of a large number of compositions under identical conditions. On a single substrate, around 50 samples can be produced simultaneously, each with varied composition.
This capability to systematically sweep the compositional space was central to identifying combinations that transform magnetization, inducing a preferred direction and significantly increasing the observed magnetic anisotropy.
The method also favors reproducibility and direct comparison between samples, accelerating the identification of trends and relationships between chemical composition, crystal structure, and magnetic properties, even with small variations.
Key Findings And Performance Without Rare Earths
The team synthesized the first high-entropy borides in the C16 structure using abundant 3d transition metals, those from the first row of the d-block of the periodic table, establishing a new class of ordered high-entropy magnetic materials.
By introducing multiple 3d transition metals and exploring the compositional space with combinatorial co-sputtering, the researchers increased anisotropy, causing magnetization to point in a preferred direction with significantly greater intensity.
Recently discovered quinary compositions exhibited strong magnetic anisotropy, approaching that of rare earth permanent magnets and exceeding previously reported values for rare earth-free high-entropy materials, a result considered a record in this context.
Density functional theory calculations confirmed the experimental trends and identified the optimized electronic structure as the origin of the increased anisotropy, highlighting valence electron concentration and effective magnetic moment.
Agreement Between Theory And Experiment And Next Steps
The agreement between theory and experiment reinforces the robustness of the approach and validates the role of electronic structure in controlling anisotropy. These findings provide clear guidelines for the rational design of new magnets.
According to Gen Yin, the team continues to explore even better permanent magnets and recording media with different compositions and underlying crystal structures. The use of machine learning is cited as a tool to accelerate discoveries.
This combination of combinatorial synthesis, theoretical modeling, and computational techniques aims to expand the explored space, quickly identifying compositions with superior magnetic properties adaptable to different applications.
Despite the focus on magnetism, the work also highlights the largely unexplored potential of ordered high-entropy materials as a platform for advanced functional properties beyond this domain, opening new avenues for research.
Impact And Applications In Sustainable Magnetic Technologies
The results establish a high-entropy synthesis strategy aided by boron to achieve strong magnetic anisotropy using only elements abundant on Earth. This approach has direct implications for sustainability and supply security.
The developed materials are especially promising for applications requiring high anisotropy, such as heat-assisted magnetic recording media, spintronic devices, and magnetic tunnel junctions, in addition to energy-efficient permanent magnets.
By demonstrating that it is possible to achieve high anisotropy without rare earth elements, the research opens new pathways for sustainable magnetic technologies, with potential impact on clean energy, consumer electronics, and industrial systems.
Beyond magnetism, the study highlights the vast potential of ordered high-entropy materials as a discovery platform, suggesting that other advanced functional properties may emerge from this compositional space still underexplored, even with some remaining technical challenges.
This article was based on material released by Georgetown University and the results of the study published in the scientific journal Advanced Materials, as synthesized by the Phys.org portal.
Uai cadê meu comentário…
PQP se forem redigir um relatório técnico específico com essa(nem.I(inteligência)-nem.A(artificial) explicando essa enxurrada verbal acima; será que ainda tem alguém com o mínimo de conhecimento gramatical…