Pressing a tiny crystal between two titanium plates was enough to shift the magnetic makeup of manganese telluride and iron sulfide, two materials at the center of research on altermagnets. Neutron diffraction at Oak Ridge National Laboratory’s Spallation Neutron Source showed that the strain changed how the crystal’s magnetic domains were populated. The experiments are described in two papers, one in Physical Review X and one in Advanced Materials.
Tech news worth reading: Get Techpresso, the daily email with the most interesting tech news and insights, read by 400,000+ professionals from Google, Apple and OpenAI.
We may earn a commission if you sign up.
Pengcheng Dai of Rice University, a former Oak Ridge neutron scientist and senior author on both, said that controlling the domains gives researchers a direct handle on how electrons move through the material. Feng Ye, an Oak Ridge neutron scientist and co-author on both papers, described the technique as a small mechanical squeeze between two plates that can expose entirely new magnetic behavior.
Altermagnets and the domain problem
An altermagnet is a magnetic state in which neighboring atoms carry opposite spins, so the material has zero net magnetization, yet its electronic bands are split by spin in a way that resembles a ferromagnet. That mix draws interest for spintronics, which uses an electron’s spin as well as its charge to store and process information. ScienceDaily’s version of the story mentions possible links to wireless communication and quantum computing.
The obstacle is domains. A crystal divides into regions with particular magnetic arrangements, and if different domains point different ways their electrical effects can cancel. The Oak Ridge team argues that mechanical strain could be a simple way to favor some domains over others and steer electron flow without changing the chemistry. The ORNL news article by Sumner S. Brown Gibbs appeared on Oct. 27, and ScienceDaily republished the story on Nov. 4.
Dai is a physicist at Rice University who formerly worked as a neutron scientist at Oak Ridge, and the collaboration spans a university and a national laboratory, with Ye on the Oak Ridge side. The Oak Ridge article also names ORNL researchers Douglas L. Abernathy and Matthew B. Stone, and the author lists carry many more names, among them Emilia Morosan, Qimiao Si, Rafael M. Fernandes and Jiun-Haw Chu.
Uniaxial strain, titanium plates and neutron beams
Each experiment compressed a small crystal in one direction, a setup called uniaxial strain. The team used neutron diffraction to look inside, because neutrons carry a magnetic moment and scatter from the arrangement of magnetic moments in a crystal. The Spallation Neutron Source is an accelerator-based facility at Oak Ridge that produces intense pulsed neutron beams as a Department of Energy user facility.
The researchers also measured the anomalous Hall effect, a sideways voltage that appears without an external magnetic field. Applied strain altered that electrical signal, which tied the change in domain populations to a change in how the material conducts. Ye said neutron scattering plays a critical role in revealing the underlying change in magnetism.
The two papers split the materials between them. The Physical Review X paper carries the name “Strain-Tunable Anomalous Hall Effect in Hexagonal MnTe,” and the Advanced Materials paper carries the name “Uniaxial Strain Tuned Magnetism of the Altermagnet Candidate H-FeS.” Iron sulfide is therefore described as a candidate, while manganese telluride is treated as an established example.
The force involved is described only as gentle. The ScienceDaily report says the crystals were gently compressed, and the Oak Ridge article calls the effect a small mechanical squeeze The wording points to a modest mechanical input compared with changing a material’s chemistry. The Spallation Neutron Source is a Department of Energy Office of Science user facility, open to outside research groups.
Iron sulfide, Berry curvature and an unsettled explanation
A Rice University release on EurekAlert dated Aug. 13 adds detail on the iron sulfide result. Compressing a hexagonal FeS crystal weakened both its tiny net magnetic moment and its anomalous Hall effect, while the larger magnetic order stayed essentially the same. Neutron scattering showed that pressure shifts which magnetic orientations are most common, though the basic structure holds.
Dai said the two effects shrink together when the crystal is squeezed in one direction, which points to a tight link between them. First author Weiliang Yao added a caution: the team is not saying the electronic explanation is wrong, and the Berry curvature account of the electrical signal was not ruled out. That leaves the mechanism partly open. The data show that strain and the electrical signal move in step, but the physics that ties them together has more than one candidate. On the practical side, Dai said that for any application, control is essential,.
None of the sources provide numbers for the pressure applied, the temperatures used or the size of the Hall signal, so the scale of the effect cannot be judged from the summaries. Those figures sit in the Physical Review X and Advanced Materials papers, whose journal pages could not be loaded for this article. What the Oak Ridge work establishes is the principle: mechanical strain can reorganize the magnetic domains in these materials, and neutrons can watch it happen.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
Tech news worth reading: Get Techpresso →
We may earn a commission if you sign up.
More from Morning Overview
- Lake Powell sank to a record 3,517 feet, nearing the level that stops Glen Canyon Dam’s turbines
- Seven of Earth’s nine planetary boundaries are breached, and all seven are worsening
- The NSA says three phone features should be off whenever you aren’t using them
- Hurricane Hunter radar shows four warning signs that a tropical cyclone is about to strengthen, a University of Miami study found
