MIT scientists have developed a groundbreaking magnetizing laser in new research that could have significant ramifications for highly efficient and resilient data storage solutions. Using only light, the team of MIT physicists altered material at the atomic level.
Ordinary commercial magnets are ferromagnets, composed of materials whose atoms spin in the same direction, making them susceptible to the pull of an external magnetic field. Antiferromagnets, by contrast, have atoms that spin alternately in opposite directions. This opposing spin cancels out any attraction to external magnetic fields.
An antiferromagnetic memory chip would record information directly onto its atoms. The manufacturing process involves dividing the chip into microscopic “domains,” where the spin orientation of an atom represents either a “1” or “0” in traditional binary code. Unlike traditional magnetic storage, antiferromagnetic memory devices would not be vulnerable to interference from stray magnetic fields, a significant weakness of conventional systems.
Additionally, these devices could be produced in much smaller form factors than current magnetic memory systems. However, achieving reliable fine control over magnetic switching has long been a major hurdle to realizing such resilient storage devices.
“Antiferromagnetic materials are robust and not influenced by unwanted stray magnetic fields,” said Nuh Gedik, an MIT Donner Professor of Physics, in a recent statement. “However, this robustness is a double-edged sword; their insensitivity to weak magnetic fields makes these materials difficult to control.”
Material Phenomena
Gedik’s team focuses on creating exotic atomic phenomena by developing new techniques to manipulate quantum materials. The interaction between a material’s atomic spins affects the vibration of its atoms. The team theorized that stimulating the atoms with oscillations matching their natural vibrations could push the spins out of alignment. This method would force the atoms to develop a larger spin in one direction, creating a preferred, infinitely magnetized state.
“In general, we excite materials with light to learn more about what holds them together fundamentally,” Gedik recently said “For instance, why is this material an antiferromagnet, and is there a way to perturb microscopic interactions such that it turns into a ferromagnet?”
Laser Magnetism
Using a terahertz laser that oscillates over one trillion times per second, the researchers manipulated the atoms in an antiferromagnetic material. The laser was finely tuned to alter the spins of the atoms, pushing them into a new magnetic state. This approach represents an entirely new method for controlling and switching antiferromagnetic materials, a crucial step for future information storage and processing technologies.
The researchers conducted their experiments on a sample of FePS3 synthesized by Seoul National University. FePS3 enters an antiferromagnetic phase at temperatures close to 118 Kelvin (-247 degrees Fahrenheit). The MIT team cooled the sample below this temperature in a vacuum chamber. Using an organic crystal to focus terahertz frequencies, they directed a beam of near-infrared light at the sample.
Demonstrating Magnetic Switching
To confirm that their method was responsible for the transition, the researchers also aimed two additional near-infrared lasers at the sample with opposite polarization. If the terahertz pulse were not the cause, there would have been no change in the transmitted intensity. Repeating the process multiple times, the terahertz pulse consistently produced the desired effect. The team was particularly intrigued by how long the transition persisted even after the laser was turned off.
“Generally, such antiferromagnetic materials are not easy to control,” Gedik says. “Now we have some knobs to be able to tune and tweak them.”
The paper “Terahertz Field-Induced Metastable Magnetization Near Criticality in FePS3” appeared on December 18, 2024 in the Nature.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.