Finding Has Significant Technological Applications
Scientists at the University of Minnesota have reported direct observation of magnon-phonon coupling in time and frequency domains under femtosecond laser excitation. Based on their observations, the team have also proposed a theoretical model explaining the physical mechanism underlying this strain-spin interaction. The results of their work are reported in “High-frequency magnetoacoustic resonance through strain-spin coupling in perpendicular magnetic multilayers,” published in Science Advances. The work is significant for the impact it could have on applications in cloud storage, and spintronic devices.
The research was conducted by an interdisciplinary team of researchers working in close collaboration over the past three years. Dr. Delin Zhang and Distinguished McKnight University Professor of Electrical and Computer Engineering Jian-Ping Wang designed and synthesized the samples and carried out the magnetic measurements.
Dr. Jie Zhang, Dr. Dustin Lattery, an alumnus of the Dept. of Mechanical Engineering, and Prof. Xiaojia Wang led the ultra fast magnetic dynamic measurement and characterization using an ultra fast laser setup. Dr. Tao Qu, an alumnus of the School of Physics and Astronomy, and Prof. Randall Victora carried out the theoretical calculations and predictions. The work has been supported by the CSPIN center, one of the SRC-DARPA STARnet centers.
SIGNIFICANCE OF THE STUDY
Most studies on magnon-phonon coupling have been conducted on materials that are unsuitable for spintronic applications. And there have not been experimental demonstrations of either magnon-phonon coupling, or ultra high frequency magnetoacoustic resonance in materials with perpendicular magnetic anisotropy (PMA). The present research addresses this by using Cobalt-Palladium multilayers as these materials have high perpendicular magnetic anisotropy (PMA), and a relatively large magnetostriction coefficient. These characteristics make them potentially valuable for technological applications, and serve as an ideal platform for investigating the magnon-phonon coupling.
The study authors have reported an extremely high frequency (EHF) magnetoacoustic resonance up to 60 GHz in the Cobalt-Palladium multilayer from the strong magnon-phonon coupling that resulted from excitation by femtosecond laser pulses. The present research holds twofold significance: it opens up a potential pathway to enabling an EHF magnetoacoustic resonance through the magnon-phonon coupling, and suggests the possibility of ultra high-speed strain-assisted magnetization switching in a technologically relevant magnetic system. Additionally, the team have developed a theoretical model that explains the physical mechanism of magnetoacoustic resonance that follows the strain-spin interaction within an energy viewpoint.
Taking the results of their research to the realm of application, the demonstration offers an approach to meeting future technological needs of high speed and highly compact memory. The work is significant for the impact it could have on applications in cloud storage, advanced spin memory, logic, and other spintronic devices.