Japan Atomic Energy Agency discovers magnetic "strong-weak waves" in uranium semiconductor

The Japan Atomic Energy Agency announced on August 21 that its research team has discovered a special magnetic structure in the layered uranium semiconductor α-UTe3 (α-uranium tritelluride): the magnetism of uranium atoms not only alternates in opposite directions, but its magnetization intensity also periodically strengthens and weakens depending on the crystal position, forming a state resembling “strong-weak waves.”

α-UTe3 is composed of uranium and tellurium atoms and belongs to van der Waals layered materials, where atomic layers are stacked through weak interlayer forces. Using high-quality α-UTe3 single crystals, the research team analyzed its low-temperature magnetic structure through resistivity, specific heat, and magnetization measurements, as well as nuclear magnetic resonance and single-crystal neutron diffraction techniques. The results showed that this material exhibits poor electrical conductivity, classifying it as a semiconductor, and displays antiferromagnetism below approximately 5 kelvin.

In conventional antiferromagnets, adjacent magnetic moments point in opposite directions and are roughly equal in magnitude. However, this study found that in α-UTe3, the magnetic moments of uranium atoms are oriented along the crystal's a-axis, alternating in direction along the uranium atom chains arranged along the b-axis, while the magnitude of the magnetic moments is not fixed but periodically fluctuates with spatial position. Since this magnetic periodicity does not match the atomic arrangement periodicity, the research team identified it as “mismatched amplitude-modulated antiferromagnetism.”

The researchers noted that such states with periodically varying magnetization intensity are typically more common in metallic materials, because electrons in metals can move within the crystal lattice. In semiconductors like α-UTe3, however, the electrons carrying magnetism remain primarily localized near uranium atoms, and it has traditionally been considered more likely that the magnetic intensity of each atom remains relatively constant. Therefore, this discovery expands the understanding of magnetic ordering states in semiconductors.

The research team believes that the strong directional nature of uranium atom magnetism in α-UTe3, combined with the chain-like and isosceles triangular arrangement of uranium atoms leading to competing magnetic interactions, may jointly contribute to the emergence of the magnetic “strong-weak waves.”

The findings were published on August 7, 2026, in the American Physical Society journal *Physical Review B* and were selected as an Editors' Suggestion. The research team stated that the next step is to investigate how the period of these magnetic “strong-weak waves” and the temperature at which antiferromagnetism appears change when the crystal is thinned, other elements are intercalated between layers, or pressure is applied, in order to explore new methods for controlling the magnetism of layered magnetic materials.