A team of researchers has found new evidence that an unusual type of magnetism may exist in an ultrathin quantum material, a discovery that could eventually help create smaller, faster and more energy-efficient computer memory.
The study, led by researchers from Rice University together with collaborators from the University of Minnesota and the Paul Scherrer Institute in Switzerland, focused on a material called ruthenium dioxide.
Their findings were published in Science Advances.
Magnetism plays an essential role in many modern technologies, from hard drives to sensors and computer memory.
In recent years, scientists have become excited about a newly proposed form of magnetism known as altermagnetism.
Although it is still being explored, this new magnetic state could combine some of the best features of existing magnetic materials, making it highly attractive for future electronic devices and spintronics, a technology that uses the spin of electrons rather than just their electrical charge.
Ruthenium dioxide was one of the first materials suggested as a possible example of altermagnetism.
However, previous studies of the material in its normal, bulk form found no convincing evidence that it was magnetic.
The new research took a different approach by studying the material in an ultrathin form. Instead of examining a large crystal, the researchers created a film that was only a few atoms thick. They discovered that shrinking the material to this extremely thin form changed its behavior in an important way.
To investigate the material, the scientists measured its spin texture, which describes how the spins of electrons are arranged. Electron spins act like tiny magnetic needles, and their patterns reveal whether a material is magnetic and what type of magnetism it has.
The team used a highly specialized technique called spin-resolved angle-resolved photoemission spectroscopy. While the name is complicated, the method essentially allows scientists to map the behavior of electrons inside a material with remarkable detail.
After carefully analyzing the results and comparing them with theoretical calculations, the researchers found spin patterns that matched what would be expected from an unconventional magnetic state similar to altermagnetism.
The researchers also discovered that this unusual behavior only appeared when the ultrathin material was placed under lattice strain. Lattice strain slightly changes the spacing between atoms, similar to gently stretching or squeezing a material. Without this strain, the electron spins no longer showed signs of the new magnetic state.
This finding suggests that scientists may be able to switch or adjust the magnetic behavior simply by controlling the amount of strain in the material. Such precise control could become valuable when designing future memory devices and spintronic technologies that are faster and use less energy than today’s electronics.
The work also highlights how complex quantum materials can be. Ruthenium dioxide has puzzled scientists for years because its bulk form appeared to be nonmagnetic, yet its ultrathin version behaves very differently under the right conditions.
According to the researchers, producing high-quality ultrathin films and making extremely careful measurements were both essential for revealing these hidden properties.
Although much more research is needed before the discovery can be turned into practical technology, the study provides a promising new direction for understanding quantum materials and developing the next generation of computer memory and electronic devices.
