Rice Scientists Find New Method to Control Electron Flow in Altermagnet

Altermagnetism, a recently recognized form of magnetism that could reshape the future of computer memory, has taken a significant step toward practical control. Researchers at Rice University have used mechanical strain to force hexagonal manganese telluride, or MnTe, into a single magnetic domain, allowing them to directly identify its underlying magnetic structure. The result, reported in Physical Review X, also revealed an unusually sharp anomalous Hall signal and demonstrated that the electrical response of the material can be reversed through strain. The discovery offers a new way to manipulate information without relying solely on temperature or conventional magnetic fields, two approaches that can be energetically expensive or difficult to integrate into miniature electronic devices.

For decades, magnetism in electronic materials has broadly been understood through two dominant categories. Ferromagnets contain magnetic moments that align in the same direction, producing a strong net magnetic field. Antiferromagnets contain neighboring moments that point in opposite directions, canceling much of the overall magnetization. Altermagnets share some characteristics with both, but their magnetic moments follow a distinct symmetry pattern in which opposite-spin states are related to the crystal’s spatial rotations. This arrangement can generate spin-polarized electronic behavior without the large stray magnetic fields associated with ferromagnets. In principle, altermagnets could support rapid spin transport while producing less heat and electromagnetic interference, making them attractive for high-density memory and next-generation computing.

The challenge is that altermagnetic materials do not normally present researchers with a single, easily readable magnetic configuration. Hexagonal MnTe tends to divide into multiple magnetic domains. Each domain contains an internally ordered group of magnetic moments, but neighboring domains can point in different directions while remaining equally compatible with the threefold rotational symmetry of the crystal lattice. When a measurement captures signals from all of these regions at once, the contributions overlap. Several different magnetic structures can then produce data that appear nearly identical, making it difficult to distinguish the material’s intrinsic behavior from the averaged response of its domains.

Rice physicist Pengcheng Dai and his collaborators addressed this problem by applying uniaxial strain, stretching the MnTe crystal preferentially along one direction. That controlled distortion breaks the balance between equivalent orientations and favors one magnetic arrangement over the others. The material consequently enters a single-domain state, removing the overlapping signals that previously obscured its magnetic structure. Rather than changing the magnetic interactions dramatically, the strain acts as a symmetry-breaking control knob. This is important because it gives scientists a way to select and study one configuration at a time while preserving the fundamental properties that make MnTe an altermagnetic candidate.

Once the researchers isolated the single domain, they could resolve the magnetic structure with much greater clarity. The experiment also exposed a remarkably sharp feature in the anomalous Hall effect, a phenomenon in which a voltage develops perpendicular to the direction of an applied electrical current. In ordinary Hall measurements, this sideways voltage is generated by an external magnetic field. The anomalous Hall effect can arise from the internal magnetic order and the quantum geometry of the electronic bands, even when the material has little net magnetization. Observing a sharp feature in MnTe’s Hall response provides an electrical signature of its unusual magnetic state and suggests that the material could translate changes in magnetic order directly into readable electronic signals.

The behavior became even more striking at temperatures near 230 kelvin, approximately minus 45 degrees Fahrenheit. At this low temperature, adjusting the direction and magnitude of the uniaxial strain could reverse the polarity of the anomalous Hall effect. In practical terms, the transverse voltage changed sign, indicating that the direction of the relevant charge response had been switched. The researchers do not attribute this reversal primarily to a large change in the magnetic interactions themselves. Instead, their interpretation points to strain-induced changes in the Berry curvature, a quantum-mechanical property of electronic energy bands that acts like a momentum-space magnetic field and can deflect charge carriers as they move through a crystal.

Berry curvature is especially important in modern materials research because it links the geometry of electronic wave functions to measurable transport effects. When electrons travel through a band structure with nonzero Berry curvature, their motion can acquire an additional transverse component, producing phenomena such as the anomalous Hall effect. In MnTe, uniaxial strain changes the crystal symmetry and therefore modifies the electronic band geometry. Even a modest structural distortion can redistribute the Berry curvature across momentum space, altering the magnitude or sign of the Hall signal. This mechanism gives researchers a way to control electrical transport without needing to heat the material or apply a strong magnetic field, potentially reducing energy consumption in future devices.

The scale of the effect is notable. The Rice team’s calculations indicate that a 1 percent change in strain can produce a response comparable to changing the temperature by roughly 150 kelvin. Temperature is commonly used to tune magnetic and electronic properties, but it is rarely convenient for everyday electronics. Heating and cooling consume energy, slow operation and can damage sensitive components. Mechanical strain, by contrast, can potentially be generated locally using piezoelectric layers, nanoscale actuators or engineered interfaces between different materials. If this approach can be translated into thin films and integrated circuits, a small structural adjustment could switch a magnetic or electrical state while avoiding the substantial thermal costs associated with conventional control methods.

The findings could therefore influence the design of spintronic technologies, which use electron spin and magnetic order rather than charge alone to store and process information. Altermagnets may offer fast spin-polarized currents, strong internal responses and minimal stray fields, combining advantages that are usually separated between ferromagnets and antiferromagnets. A strain-controlled anomalous Hall signal could serve as a compact readout or switching mechanism for memory cells, sensors and logic elements. Such applications remain developmental, and major challenges—including room-temperature operation, fabrication uniformity, durability and scalable strain control—must still be solved. Nevertheless, demonstrating a clear single-domain state and reversible Hall response in MnTe gives scientists an essential foundation for learning how altermagnets behave and how their quantum properties might be harnessed.

The study represents a shift from merely identifying altermagnetic materials to actively controlling them. By turning mechanical deformation into an electronic and magnetic tuning tool, the researchers have shown that crystal symmetry, domain structure and Berry curvature can be manipulated as parts of one connected system. Future devices based on this principle could operate at higher frequencies, generate less heat and pack more memory into smaller spaces. For consumers, that could eventually mean faster phones and computers with longer battery life during demanding tasks. The technology is not yet ready for commercial hardware, but the ability to isolate and control a single altermagnetic domain brings the field closer to converting an intriguing quantum phenomenon into a practical platform for information technology.

Web References: https://profiles.rice.edu/faculty/pengcheng-dai ; https://journals.aps.org/prx/accepted/10.1103/589s-s1yy

References: Physical Review X, DOI: 10.1103/589s-s1yy

Keywords

Altermagnetism, manganese telluride, MnTe, anomalous Hall effect, Berry curvature, magnetic domains, uniaxial strain, spintronics, quantum magnetism, magnetic memory