“Hearst Magazines and Yahoo may earn commission or revenue from some items via these links.” Scientists have successfully triggered a novel magnetic state in an antiferromagnet solely using light, a development with significant implications for data storage technologies. By employing a terahertz laser, researchers were able to resonate atoms at the same frequency as the material’s phonons, displacing it from its antiferromagnetic state. This altered state endured for several milliseconds, a notable extension compared to the usual picosecond timeframe, offering the research team additional opportunities to investigate and manipulate the magnetic properties of antiferromagnets. The application of lasers has proven to be an effective method for groundbreaking scientific discoveries and advancements. While oversimplified, directing a laser at a solar sail could potentially propel humanity towards another star system, and the initiation of the first bootstrapping fusion reaction in human history involved firing multiple lasers at a capsule of hydrogen isotopes. Now, an international group of scientists, including many from MIT, aims to contribute another significant breakthrough. Described in a recent publication in the journal Nature, these experts in condensed-matter physics successfully altered the magnetic state of an antiferromagnetic material using light, specifically a laser. This breakthrough could revolutionize the design of smaller, faster, and more energy-efficient memory chips and pave the way for further exploration of this new magnetic state. To elaborate on some terms: while ferromagnets have atoms with aligned spins that easily respond to external magnetic fields, antiferromagnets consist of atoms with alternating spins that neutralize each other’s magnetic effects, resulting in zero net magnetization. For data storage purposes, this quality is advantageous rather than detrimental. “Antiferromagnetic materials are sturdy and impervious to stray magnetic fields,” noted Nuh Gedik, the study’s senior author and an MIT professor. “However, their resilience is a double-edged sword; their resistance to weak magnetic fields makes these materials challenging to control. Now, we have methods to adjust and manipulate them.” This approach involves utilizing a near-infrared terahertz pulse transmitted through an organic crystal to convert light into terahertz frequencies. When the material, iron phosphorus trisulfide (FePS3), is cooled to approximately 118 Kelvin (247 degrees Fahrenheit), it transitions to an antiferromagnetic state. Upon exposure to a terahertz laser, the atoms resonate with the material’s collective vibrations (phonons), disrupting FePS3’s antiferromagnetic equilibrium and establishing a new magnetic state. “The terahertz pulse is the means through which we induce a change in the sample,” explained Tianchuang Luo from MIT. “It’s akin to ‘writing’ a new state into the sample.” Previous experiments have shown that such magnetic states typically endure for a mere fraction of a second, much briefer than the blink of an eye. However, the researchers have observed that this altered state persisted for “several milliseconds,” even
The researchers are studying their manipulation of this antiferromagnetic material. “In general, we use light to excite materials in order to gain a deeper understanding of their fundamental structure,” Gedik stated in a press release. “For example, what causes this material to exhibit antiferromagnetic properties, and is it possible to alter the microscopic interactions in a way that would transition it into a ferromagnet?”
