Using the phenomenon of magnetorotational coupling, the researchers were able to completely suppress the movement of sound energy in one direction inside the material, which opens up the possibility of creating «acoustic diode».
Devices called rectifiers are essential in the advancement of technology. The most famous are electronic diodes that convert alternating current into direct current, without which electrification would be impossible. A team from the Japan Institute for Physical and Chemical Research (RIKEN) found that sound waves can be controlled in a similar way.
Studying the propagation of surface acoustic waves in a magnetic film, they observed their interaction with spin waves (disturbances in magnetic fields inside the material) through magnetorotational coupling. This was the first experimental confirmation of such an influence since the assumption of its existence more than 40 years ago..
The team found that this interaction occurs simultaneously with the well-studied magnetoelastic coupling, but at a different intensity. When the sample’s magnetization rotated in the same direction as the surface acoustic waves, their energy was transferred to the spin waves more efficiently, increasing the rotation of the magnetization.
In fact, the researchers were able to identify a unidirectional coupling configuration in which only unidirectional wave energy could be transferred to the rotation of the magnetization. They also noticed that this straightening effect was more pronounced when the material exhibited magnetic anisotropy..
According to scientists, in the future they intend to use these principles to create «acoustic diode», in which sound energy will only be transmitted in one direction and blocked in the other. Since this happens at microwave frequencies, such rectifiers can be used in 5G and other telecommunication technologies..
Recall that last year, engineers created the world’s first sound projector that can track the movement of a specific person and create a sound sphere next to him to transmit individual audio messages..
text: Ilya Bauer, photo: Shutterstock
Scientists have discovered the principles of creating a sound diode