MIT physicists have found an innovative way to create a new magnetic state in a material using only light.
By using a special type of laser called a terahertz laser, which oscillates more than a trillion times per second, they were able to nudge the material’s atoms into a magnetic state that lasts far longer than expected.
This breakthrough could pave the way for more efficient data storage and memory chip technologies.
The research, published in Nature, focuses on a material called FePS3. This material becomes an antiferromagnet when cooled to extremely low temperatures.
Antiferromagnets are unique because their atomic spins alternate directions—up, down, up, down—canceling each other out and creating no overall magnetism.
This makes antiferromagnets immune to interference from stray magnetic fields, which could make them ideal for memory chips that are more stable and compact than current technologies.
However, controlling antiferromagnets has been a major challenge because their balanced spins are hard to disrupt.
MIT researchers found a way around this problem by using terahertz light to directly interact with the material’s atoms.
“When atoms in a solid vibrate, they have a natural frequency, like tiny springs moving back and forth,” explained Alexander von Hoegen, a researcher on the team.
The team realized that if they used a terahertz laser tuned to the same frequency as the atoms’ vibrations, it could also affect the spins of the atoms, knocking them out of their balanced state. This process created a preferred spin orientation, effectively magnetizing the material.
To test their theory, the scientists cooled the FePS3 sample to below -247 degrees Fahrenheit (118 kelvins) and aimed terahertz pulses at it.
These pulses were created by transforming near-infrared light into terahertz frequencies using a special crystal. The team then used two lasers with opposite circular polarizations to check if the material’s magnetic state had changed.
If the terahertz pulse had worked, the intensity of the transmitted lasers would differ—indicating a new magnetic state.
The experiments showed that the terahertz pulse successfully switched the material into a magnetic state, which surprisingly lasted for several milliseconds, much longer than the fleeting picoseconds seen in similar studies.
“This gives us a valuable window of time to study the material’s properties and understand how to fine-tune these changes,” said Nuh Gedik, senior author of the study.
This discovery could lead to significant advancements in memory storage. A chip made from antiferromagnetic materials could store data in tiny magnetic regions, where one spin configuration represents a “0” and another represents a “1.” Such chips would be smaller, more energy-efficient, and resistant to outside interference.
“This is like ‘writing’ a new state into the material with light,” said Tianchuang Luo, another researcher on the team.
With more experiments, scientists aim to unlock the full potential of antiferromagnets for next-generation technologies. This study was supported by the U.S. Department of Energy and the Gordon and Betty Moore Foundation.
Source: MIT.
