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Georgetown University researchers have discovered a new class of strong magnets that do not rely on rare-earth or precious metals — a breakthrough that could significantly advance clean energy technologies and consumer electronics such as motors, robotics, MRI machines, data storage and smart phones.
A key figure of merit for a magnet is the ability of its magnetization to strongly prefer a specific direction, known as magnetic anisotropy, which is a cornerstone property for modern magnetic technologies.
Today, the strongest anisotropy materials for permanent magnets depend heavily on rare-earth elements, which are expensive, environmentally damaging to mine and vulnerable to supply-chain disruptions and geopolitical instability. For thin film applications, certain alloys of iron and platinum have become the materials of choice for next generation magnetic recording media, which contain precious metal platinum. Finding high-performance alternatives based on earth-abundant elements has therefore been a long-standing scientific and technological challenge.
A team led by professors Kai Liu and Gen Yin and graduate student Willie Beeson (G’25) in the Department of Physics at Georgetown University College of Arts & Sciences recently discovered a new type of strong magnets based on high entropy borides using earth-abundant transition metals and boron. The materials are both rare-earth-free and precious-metal-free, offering a compelling new strategy for sustainable magnet design. Their results are published in the journal Advanced Materials.
“We offer a sustainable approach to making strong magnets that may be used for many applications, from future magnetic recording media to permanent magnets,” said Liu, one of the senior authors of the study. “More importantly, this points to the potential to alleviate the dependence on critical materials for magnets and other applications.”
From left to right: Assistant professor of physics Gen Yin, Ph.D. student Willie Beeson (G’25) and Kai Liu, professor and McDevitt Chair in Physics, at Beeson’s thesis defense.
High-entropy alloys are materials containing five or more elements in near-equal proportions. They have recently emerged as a powerful platform for materials discovery. Their vast compositional space enables access to novel electronic structures and properties. However, most studies of such alloys focus on chemically disordered cubic structures, which are ill-suited for strong magnetic anisotropy that prefers lower crystal symmetry.
The researchers overcame this limitation by focusing on high-entropy borides, where boron promotes chemical ordering and lower-symmetry crystal structures. They targeted a crystal structure with tetragonal symmetry — imagine stretching a cube along one of its sides — called C16 phase. This structure is known in boron-based materials made from two or three elements but is largely unexplored in more complex materials.
Beeson synthesized these high-entropy borides using a combinatorial sputtering method in Liu’s lab, where atoms of the multiple target materials thoroughly mix by the time they are collected on a heated substrate. This approach also allowed rapid explorations of a large number of material compositions. On a single substrate, about 50 samples can be made simultaneously under identical conditions but with varying compositions.
Key Findings
- Discovery of a new class of strong magnets: The team realized the first high-entropy borides in the C16 crystal structure using earth-abundant 3d transition metals — those that occupy the first row of the d-block of the periodic table — establishing a new class of ordered high-entropy magnetic materials.
- Anisotropy enhancement through chemical mixing: By introducing multiple 3d transition metals and systematically exploring composition space using a combinatorial co-sputtering approach, the researchers transformed the magnetization to point to a preferred direction with a significantly larger anisotropy.
- Record-level performance without rare-earths: Newly discovered quinary boride compositions exhibit strong magnetic anisotropy approaching that of rare-earth permanent magnets and exceeding previously reported values for rare-earth-free high entropy materials.
- Theory and experiment in agreement: Density functional theory calculations confirm the experimental trends and identify optimized electronic structure, particularly valence electron concentration and effective magnetic moment, as the origin of the enhanced anisotropy.
“We’re continuing exploring even better permanent magnets or recording media with different compositions on different underlying crystal structures,” said Yin, another senior author of the study. “With the help of machine learning we are hoping to make more rapid progress.”
Impact and Applications
The results establish a boron-assisted, high-entropy synthesis strategy for achieving strong magnetic anisotropy using earth-abundant elements alone. These materials are especially promising for applications that demand high anisotropy, such as:
- Heat-assisted magnetic recording media
- Spintronic devices and magnetic tunnel junctions
- Energy-efficient, rare-earth-free permanent magnets
By demonstrating that high magnetic anisotropy can be engineered without rare-earth elements, using only abundant transition metals, this research opens new pathways toward sustainable magnetic technologies. Beyond magnetism, this work highlights the vast and largely unexplored potential of ordered high-entropy materials as a discovery platform for advanced functional properties.
The team also included postdoctoral fellows Dhritiman Bhattacharya and Dinesh Bista, and graduate student Bradley Fugetta (C’23). The work was supported in part by the National Science Foundation (NSF), 5E Advanced Materials and the Advanced Cyberinfrastructure Coordination Ecosystem Services & Support (ACCESS) program.
Beeson and Liu are co-inventors on a pending patent application on Boron-based and high-entropy magnetic materials filed by Georgetown University.
Contacts:
Kai Liu
Georgetown University, Department of Physics
Email: [email protected]
Gen Yin
Georgetown University, Department of Physics
Email: [email protected]
