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Acoustic wave in solid has two modes of propagation: the bulk acoustic wave (BAW), which propagates inside solid in the form of longitudinal or transverse wave, and the surface acoustic wave (SAW), which is generated on the surface of solid and propagates along the surface. In acoustic radio frequency (RF) technologies acoustic waves are used to intercept and process RF signals, which are typified by the rapidly developing RF filter technology. Acoustic filter has the advantages of small size, low cost, steady performance and simple fabrication, and is widely used in mobile communication and other fields. Due to the mature fabrication process and well-defined resonance frequency of acoustic device, acoustic wave has become an extremely intriguing way to manipulate magnetism and spin current, with the goal of pursuing miniaturized, ultra-fast, and energy-efficient spintronic device applications. The integration of magnetic materials into acoustic RF device also provides a new way of thinking about the methods of acoustic device modulation and performance enhancement. This review first summarizes various physical mechanisms of magneto-acoustic coupling, and then based on these mechanisms, a variety of magnetic and spin phenomena such as acoustically controlled magnetization dynamics, magnetization switching, magnetic domain wall and magnetic skyrmions generation and motion, and spin current generation are systematically introduced. In addition, the research progress of magnetic control of acoustic wave, the inverse process of acoustic control of magnetism, is discussed, including the magnetic modulation of acoustic wave parameters and nonreciprocal propagation of acoustic waves, as well as new magneto-acoustic devices developed based on this, such as SAW-based magnetic field sensors, magneto-electric antennas, and tunable filters. Finally, the possible research objectives and applications of magneto-acoustic coupling in the future are prospected. In summary, the field of magneto-acoustic coupling is still in a stage of rapid development, and a series of groundbreaking breakthroughs has been made in the last decades, and the major advances are summarized in this field. The field of magneto-acoustic coupling is expected to make further significant breakthroughs, and we hope that this review will further promote the researches of physical phenomena of the coupling between magnetism and acoustic wave, spin and lattice, and potential device applications as well.
Keywords:
magneto-elastic coupling /
acoustic control of magnetism /
magnetic control of acoustic wave /
magneto-acoustic device
Figure 4.
Detection of SAW-driven magnetization dynamics: (a) Magneto-optic method and characterization of damping factor
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; (b) NV center
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; (c) microfocused Brillouin light scattering
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; (d) X-ray magnetic circular dichroism-photoemission electron microscopy
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; (e) direct current electrical detection by anisotropic magnetoresistance rectification effect
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.
Figure 5.
Acoustic wave-assisted magnetization switching: (a) Schematic representation of the device used in SAW-assisted magnetization switching
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; (b), (c) mechanism of switching and focused SAW for small spot writing
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; (d) field-free switching induced by SAW
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; (e) SAW-assisted spin-transfer-torque switching
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; (f) SAW-assisted spin-orbit-torque switching
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.
Figure 8.
Generation of spin current by SAW: (a), (b) Acoustic spin pumping
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; (c) enhancement of acoustic spin pump by the acoustic cavity
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; (d) Rayleigh wave generates spin current by spin-rotation coupling
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; (e) shear horizontal wave generates spin current by spin-rotation coupling
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.
Figure 9.
Nonreciprocal SAW propagation induced by magneto-acoustic coupling: (a), (b) Nonreciprocity via magneto-elastic coupling
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; (c), (d) nonreciprocity via magneto-rotation coupling
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; (e) nonreciprocity via DMI
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; (f) nonreciprocity in ferromagnetic multilayers mediated by dipolar coupling
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; (g) nonreciprocity in ferromagnetic multilayers mediated by RKKY coupling
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.
Figure 10.
SAW-based magnetic field sensors: (a) Schematic diagram of Δ
E
effect
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; (b) magnetic sensor based on SAW resonator
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; (c)
S
RF
results in different directions; (d) magnetic sensor based on SAW delay line
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; (e) magnetic sensitivity by applying DC magnetic bias fields; (f) limit of detection (LOD) in the frequency range of 40 kHz from the carrier signal (148 MHz)
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.
Figure 11.
Schematic diagram of magnetoelectric antennas with different structures, including NPR (a), FBAR (b), SMR (c); (d) variation of magnetoelectric coupling coefficient of NPR structure with applied magnetic field
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; (e)
S
parameters of FBAR antenna
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; (f)
S
parameters of SMR antenna
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.
