Synopsis

Thin Films of Topological Magnets for Thermoelectric Applications

Physics 17, s66
A thin film of a topological magnet displays a large thermoelectric effect that doesn’t require an applied magnetic field—a behavior that could lead to new energy-harvesting devices.
S. Kurosawa et al. [1]

Certain ferromagnets exhibit a thermoelectric phenomenon known as the anomalous Nernst effect (ANE): they generate a voltage when simultaneously subjected to a thermal gradient and a magnetic field. Recently, researchers have demonstrated that certain “topological magnets” exhibit an ANE even in the absence of an applied magnetic field. Now Shun’ichiro Kurosawa at the University of Tokyo and colleagues have shown that a thin, crystalline film of a topological magnet, iron stannide (Fe3Sn), displays such behavior [1]. The thin film offers a promising platform for engineering heat-flux sensors and energy-harvesting devices, the researchers say.

Conventional bulk ferromagnets exhibiting the ANE typically produce voltages of less than 1 µV per Kelvin-degree gradient and require an external magnetic field (1–2 tesla). Such a large field is necessary to align the material’s magnetic domains. The thin film of Fe3Sn that Kurosawa and colleagues fabricated is a crystalline magnet with a nontrivial, or topological, electronic band structure characterized by a large “Berry curvature.” This Berry curvature, which describes how an electron’s wave function “twists” as the electron propagates through the material, induces an ANE several times larger than that of conventional magnets. What’s more, the thin film possesses a so-called magnetocrystalline anisotropy, which causes the magnetization to align along a specific direction within the film plane.

Kurosawa and colleagues’ Fe3Sn thin film is shown to display a large zero-field ANE (a few µV/K, a value comparable to or exceeding those reported for bulk materials). The researchers say that the key asset of their demonstration is the use of a material composed of inexpensive elements.

–Marric Stevens

Marric Stephens is a Corresponding Editor for Physics Magazine based in Bristol, UK.

References

  1. S. Kurosawa et al., “Large spontaneous magneto-thermoelectric effect in epitaxial thin films of the topological kagome ferromagnet Fe3Sn,” Phys. Rev. Mater. 8, 054206 (2024).

Subject Areas

Condensed Matter PhysicsElectronicsMagnetism

Related Articles

Exploring Quantum Mpemba Effects
Quantum Physics

Exploring Quantum Mpemba Effects

In the Mpemba effect, a warm liquid freezes faster than a cold one. Three studies investigate quantum versions of this effect, challenging our understanding of quantum thermodynamics. Read More »

Atomic Spreading Produces Novel Superconductors
Condensed Matter Physics

Atomic Spreading Produces Novel Superconductors

A liquid-like spreading of metal atoms on a topological material can generate a superconductor—one that might benefit quantum computing. Read More »

A New Way to Transport Spin Currents
Magnetism

A New Way to Transport Spin Currents

Spin currents carried by magnetic waves called magnons can be sent across a device without using insulating magnets—a result that could lead to spintronic devices compatible with silicon electronics. Read More »

More Articles