Coupling the waves of an electromagnetic signal—a Wi-Fi signal—with strain waves in a micrometric device is what Surface Acoustic Waves (SAW) filters do, based on the piezoelectric effect. This coupling has enabled a remarkable miniaturization of wireless communication technologies because it allows for the conversion of long wavelengths, 15 centimeters for a Wi-Fi wave, into much shorter wavelengths, few micrometers for acoustic waves (all working at the GHz range).
The interaction between “strain” and magnetization—magnetoelasticity—is receiving an increasing interest because it offers an alternative control of magnetization at the nanoscale that avoids electrical currents. An example is the efficient coupling through strain between ferroelectric and magnetic orders in multiferroics. Strain is used in spintronics as an additional degree of freedom to adjust magnetic properties. The field of ‘Straintronics’ is emerging and strain-control of functionalities might not be limited to magnetic properties.
Our project, SoundSpin, studies the coupling between surface acoustic waves (SAW) and magnetization dynamics according to the following two lines:
Line 1: Acoustic manipulation of magnetization dynamics
In this line, we will explore and exploit the coupling between acoustic waves and magnetic waves in different magnetic materials, focusing on its generation and modulation. Our proposed work consists, on the one hand, in generating large angle spin waves and sizable magnetization dynamics with SAW in different materials including Heusler alloys and 2D-magnets, and, on the other hand, in controlling spin wave propagation with SAW, aiming at the creation of functional magnonic device—a device capable to create frequency band gaps or nonreciprocal spin-wave propagation controlled by SAW.
Line 2: Acoustic generation of spins
In this line, we will study the generation of pure spin currents induced by SAW patterns. Our proposed work consists in optimizing SAW generation to obtain, on the one hand, maximal heat gradients (fast and localized) and, on the other hand, large angle magnetization precession at high frequencies. In both cases, we might generate spin currents either through the spin Seebeck effect or through the spin pumping effect.