The researchers used a terahertz laser to control magnetic spin inside antiferromagnetic materials.
By Ryan Whitwam December 23, 2024
Credit: MIT / Adam Glanzman
Scientists from MIT have been blasting magnets with lasers, which is more scientific than it sounds. Researchers working with antiferromagnetic material have devised a way to control the magnetic states of atoms with a super-fast laser. With the precise control over atomic spin demonstrated in this work, it may be possible to develop a new generation of more durable and efficient magnetic data storage.
Everyone knows what a magnet is, but what about an antiferromagnet? Magnetic materials get their attractive properties from the orientation of atomic spin. In a magnet, the spin is aligned in the same way so the material can be influenced by an external magnetic field. However, an antiferromagnet is composed of atoms with alternating spin—one pointing up, then one down, then up, and so on. This averages out to net zero magnetization.
Researchers have long believed that antiferromagnets could serve as a next-generation alternative to traditional magnetic storage media. However, the problem has always been in how you write data by switching up its magnetic states. That’s where the laser comes in.
This work relies on terahertz lasers, which oscillate more than one trillion times per second. This high-frequency light can be adapted to the natural vibrations of atoms in antiferromagnetic material. Hitting atoms with this laser can nudge them into new magnetic states that persist after the laser is deactivated. The researchers say it’s possible to align atomic spins so precisely that you can “write” data to a specific domain. For example, a spin combination of up-down could be a “0” bit, and down-up can signify the classical bit “
According to the study, which has been published in the journal Nature, the team used a common antiferromagnetic material called Iron phosphorus trisulfide (FePS3). This material transitions to an antiferromagnet at a temperature of -247 degrees Fahrenheit (118 Kelvin). The team sought to influence this process by use of the high-frequency laser. Most solid materials have collective vibrations, called phonons, in the terahertz range. By exciting atoms in this range, the spin can be shifted to create what are essentially tiny magnets within the antiferromagnet that don’t go poof the instant the laser shuts off.
Study authors Tianchuang Luo, Nuh Gedik, and Alexander von Hoegen tinkering with terahertz lasers. Credit: MIT / Adam Glanzman
“The idea is that you can kill two birds with one stone: You excite the atoms’ terahertz vibrations, which also couples to the spins,” says study co-author Nuh Gedik. Researchers have done this before, but the difference with the new work at MIT is that these magnetic properties persist after the laser is deactivated. Previous light-induced transitions have only lasted a few picoseconds.
Showing that this is possible in the lab is an important first step, but we’re a long way from using antiferromagnetic materials for data storage. There’s plenty of reason to pursue this technology, though. Antiferromagnetic storage would not be vulnerable to external magnetic fields, making them much more durable. They would also be much smaller, with greater data density, and they would use very little power compared with traditional media.
https://www.extremetech.com/science/mit-physicists-control-magnetism-with-light