MIT scientists have found a new way to control magnetic states in materials, potentially paving the way for advancements in memory chip technology. The team used a terahertz laser—a light source oscillating more than a trillion times per second—to induce a durable magnetic phase in an antiferromagnetic material.
The researchers successfully shifted the atomic spins by tuning the laser to the material’s atomic vibrations, achieving a previously unattainable magnetic state.
Antiferromagnetic materials, known for their alternating atomic spins that cancel each other out, are resilient against external magnetic interference, unlike traditional ferromagnets. This makes them ideal candidates for robust data storage technologies.
However, their resistance to magnetic manipulation has been a longstanding hurdle. MIT’s breakthrough demonstrates a viable approach to overcoming this challenge, marking a critical step toward integrating antiferromagnets into compact, energy-efficient memory chips.
A new magnetic state
The research team, led by Nuh Gedik, Donner Professor of Physics at MIT, explored how light could influence the magnetic properties of FePS3, a material that becomes antiferromagnetic at temperatures below 118 Kelvin (-247°F). To manipulate its state, they used a terahertz laser tuned to match the frequency of the material’s atomic vibrations, or phonons.
In solids, atoms are connected by spring-like bonds that vibrate at characteristic frequencies. These vibrations influence how atomic spins interact. By stimulating the phonons with terahertz light, the team disrupted the material’s balanced spin alignment, nudging it into a state with a net magnetization—a dramatic shift from its inherent zero-magnetization nature.
“In general, we excite materials with light to learn more about what holds them together fundamentally,” Gedik says. “For instance, why is this material an antiferromagnet, and is there a way to perturb microscopic interactions such that it turns into a ferromagnet?”
To test their hypothesis, the team cooled a sample of FePS3 and exposed it to a terahertz pulse generated by transforming near-infrared light through an organic crystal. They then verified the magnetic shift by analyzing the sample with polarized infrared lasers. A detectable change in the transmitted laser intensities confirmed that the material had transitioned to a new magnetic state.
Remarkably, this induced state persisted for several milliseconds—an exceptionally long duration compared to the picosecond (trillionth of a second) timescales typically observed in light-induced phase transitions. This window provides researchers with ample time to probe the properties of the new state and identify further ways to control antiferromagnetic materials.
Implications for data storage
Antiferromagnetic materials have long been considered potential game-changers for information storage. Their alternating spin configurations could represent binary data, with one arrangement encoding “0” and another encoding “1.” This data would remain stable against external magnetic influences, offering a more robust alternative to existing magnetic storage technologies.
“Antiferromagnetic materials are robust and not influenced by unwanted stray magnetic fields,” says Gedik. “However, this robustness is a double-edged sword; their insensitivity to weak magnetic fields makes these materials difficult to control.”
The team’s ability to reliably switch an antiferromagnet to a new state using light opens the door to practical applications. These materials could form the basis of next-generation memory chips capable of storing and processing more data while consuming less energy and occupying minimal space.
As Gedik’s group continues to refine their methods, they hope to further optimize light-induced phase transitions and explore new ways to tweak antiferromagnetic properties. This could ultimately lead to the development of more sustainable and efficient memory storage systems, transforming the landscape of data processing and technology.
The study has been published in Nature.
