Researchers Uncover Novel Approaches to Stimulate Spin Waves Using Intense Infrared Light

As the demand for computing resources continues to grow at a rapid pace, scientists and engineers are actively seeking ways to develop faster systems for processing information. One potential solution involves utilizing patterns of electron spins, known as spin waves, to transfer and process information much more quickly than traditional computers. However, a significant challenge has been the manipulation of these ultrafast spin waves to perform useful tasks.

In a groundbreaking advancement, a team of researchers from The University of Texas at Austin and MIT has devised an innovative technique to precisely manipulate these ultrafast spin waves using customized light pulses. The details of their findings can be found in two studies published in Nature Physics. The research was led by Zhuquan Zhang, a graduate student from MIT, Frank Gao, a postdoctoral researcher from the University of Texas at Austin, Keith Nelson, a professor of chemistry at MIT, and Edoardo Baldini, an assistant professor of physics at UT Austin.

Magnetic data recording technology plays a crucial role in our smartphones, the internet, and cloud computing by enabling the storage and retrieval of vast amounts of information. This technology relies on the manipulation of magnetic spin states (up and down) in ferromagnetic materials, which represent the binary bits “0” and “1.” These spins are essentially tiny magnets, and their alignment determines the magnetic properties of the material.

When researchers illuminate a specific group of atoms in these materials with light, it causes their spins to oscillate in a pattern that propagates through neighboring atoms, resembling waves on a pond when a stone is dropped. This phenomenon is known as a spin wave.

In contrast to conventional data storage materials, a unique category of magnetic materials called antiferromagnets possess spins that are aligned in opposite directions. These materials exhibit spin waves that are typically much faster than those found in ferromagnets, making them promising for future high-speed information processing architectures.

The researchers conducted experiments using an antiferromagnet known as an orthoferrite. This material is characterized by two distinct spin waves that typically do not interact with each other. However, by utilizing terahertz (THz) light, which is not visible to the human eye and operates at extreme infrared frequencies, the researchers successfully induced interaction between these spin waves.

One of the papers presented the surprising discovery that by using intense THz fields to excite a spin wave at a specific frequency, another spin wave at a higher frequency can be initiated. This phenomenon is akin to the harmonic overtones produced when a guitar string is plucked.

“This finding truly caught us off guard,” remarked Zhang. “It indicated that we have the ability to nonlinearly control the flow of energy within these magnetic systems.”

In the other paper, the researchers observed that exciting two different spin waves can give rise to a new hybrid spin wave. Baldini expressed excitement about this discovery as it has the potential to propel the technology beyond spintronics into a new domain known as magnonics. In spintronics, information is carried by the spin of individual electrons, whereas in magnonics, information is conveyed through spin waves, also referred to as magnons.

Baldini explained that in this case, instead of using spintronics, the researchers are utilizing a collective form of spin waves that involve multiple electron spins simultaneously. This approach enables them to achieve extremely fast timescales that are not achievable in spintronics and also facilitates more efficient information transfer.

In order to conduct this groundbreaking research, the scientists devised an advanced spectrometer to investigate the interplay between different spin waves and uncover their underlying symmetries.

Gao highlighted the difficulty in detecting THz light compared to visible light, stating that without the development of this technique, these experiments would have been impossible. The technique allowed them to measure THz signals using only a single light pulse.

This article is republished from PhysORG under a Creative Commons license. Read the original article.