Researchers kickstart magnetic spin waves on a nanoscale in pursuit of low-energy computing

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An international team in Delft, Lancaster, Nijmegen, Kiev and Salerno has demonstrated a new technology that produces electromagnetic waves that propagate through materials at speeds much faster than the speed of sound.

These so-called spin waves generate much less heat than traditional currents, making them promising candidates for future computing devices with significantly reduced power consumption.

Physicists and engineers around the world are constantly thinking about ways to improve the performance of their data processing devices. Many of their ideas revolve around replacing the currents that carry signals in traditional electronics with waves. The waves are coherent excitation. That is, the information can be encoded in both the amplitude and phase of the wave. Interference and diffraction, which are natural phenomena of waves of all nature, allow the creation of so-called wave-based logic circuits, which are small components of future data processing applications.Waves pass through materials that are significantly less resistant than currents and can be significantly reduced. power consumption In future computing.

Antiferromagnetic spin wave

Electromagnetic waves, also known as spin waves, are one of the most promising candidates for wave-based logic devices. Experiments with spin waves on ordinary (iron) magnets have shown that small logic devices can be constructed without the use of electrical current. Ferromagnets are characterized by net magnetization. Thanks to the latter, it is possible to read and write magnetic information on ferromagnets with the help of an external magnetic field.

In recent years, the focus has shifted to the use of antiferromagnets. In antiferromagnetic materials, the microscopic magnetic moments (spins) of adjacent atoms are tightly coupled, alternating between the two opposite directions, eliminating the net magnetization. The presence of this alternating sequence leads to significantly higher spin wave propagation velocities and the potential for terahertz (trillion hertz) operating clock rates. However, due to the lack of magnetization, the antiferromagnet is magnetically “invisible”. It is very difficult to detect and influence the antiferromagnetic order. Practice has shown that the generation and detection of spin waves that can pass through antiferromagnetic media is even more difficult. As a result, the concept of computing based on antiferromagnetic spin waves has existed as a field of exciting opportunities that is theoretically attractive but experimentally unknown. Therefore, it is very important to find new ways to control the “magnetic moment” of antiferromagnets.

An international team of researchers is now successful in creating nanometer-sized coherents. Electromagnetic waves An antiferromagnet that moves materials at supersonic speeds.Their trick was to use ultrashort pulses Light Create and detect these spin waves. “We knew that ultrashort pulsed light could affect the magnetic properties of antiferromagnets, but the possibility of light emitting short wavelength propagating spin waves is still quite unexpected. “We did,” said Jorrit Hortensius, a researcher at Delft University of Technology. “This is because the light pulse lacks the momentum needed to generate a short wavelength or large momentum spin wave.”

Local super fast kick

It has been known for several years that ultrashort pulsed light can hold the key to producing high frequency propagating spin waves. Within picoseconds (one millionth of a second), such pulses can shake an ordered magnetic system and initiate the magnetic motion of an antiferromagnetic material. However, the excited region usually remains localized and does not support propagation. Another hidden component was needed to excite to move across the material. “Most antiferromagnetic materials are dielectrics that are transparent to visible light. Instead, they use strongly absorbed UV light, which is very close to the surface of the material, within the so-called skin depth. I’m only swinging the spin, “says researcher Dmytro Afanasiev. “The combination of ultrafast kick and strong confinement on the surface of the material turned out to be a combination that induces the propagation of antiferromagnetic spin waves.”

The wavelength of spin waves is about 100 nm, which is much smaller than the wavelength of light. Researchers believe that this may have generated even smaller spin waves, even though current instruments could not observe them. Jorrit Hortensius: “Spin waves with very short wavelengths are the most interesting for creating very compact computational elements, so I want to know what the limits are.”

This work brings the future of antiferromagnetic spin wave devices closer to reality. Lostislav Mikhaylovskiy of Lancaster University said: Antiferromagnetic material They have been considered virtually useless because they do not have magnetization. But very recently, the unique function of antiferromagnets has created a real boom in their research.We believe our findings will stimulate further research Antiferromagnetism Spin wave And finally, antiferromagnetic-based logic devices can be put to practical use. This has the potential to significantly reduce the power required for computing. ”

Spintronics: Improving electronic devices with finer spin control

For more information:
JR Hortensius et al, Coherent Spin Wave Transport in Antiferromagnets, Nature Physics (2021). DOI: 10.1038 / s41567-021-01290-4

Quote: Researchers kick-start magnetic spin waves on a nanoscale in pursuit of low-energy computing (July 29, 2021), https: // Obtained July 29, 2021 from magnetic-nanoscale-pursuit-energy.html

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Researchers kickstart magnetic spin waves on a nanoscale in pursuit of low-energy computing

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