Magnetostrictive hypersound generation by spiral magnets in the vicinity of magnetic field induced phase transition

• Magnetostrictive ultrasound generation by spiral magnets at phase transition (PT) is studied.
• Spiral magnets during PT may generate transverse sound with wavelength equal to spiral period.
• Amplitude of the sound is strictly depends on the phase transition speed.
• Microwave-to-sound transformation in the vicinity of PT is investigated as well.

In present work we have investigated magnetostrictive ultrasound generation by spiral magnets in the vicinity of magnetic field induced phase transition from spiral to collinear state. We found that such magnets may generate transverse sound waves with the wavelength equal to the spiral period. We have examined two types of spiral magnetic structures: with inhomogeneous exchange and Dzyaloshinskii–Moriya interactions. Frequency of the waves from exchange-caused spiral magnetic structure may reach some THz, while in case of Dzyaloshinskii–Moriya interaction-caused spiral it may reach some GHz. These waves will be emitted like a sound pulses. Amplitude of the waves is strictly depends on the phase transition speed. Some aspects of microwaves to hypersound transformation by spiral magnets in the vicinity of phase transition have been investigated as well. Results of the work may be interesting for investigation of phase transition kinetics as well, as for various hypersound applications.