Magnons Parametric Pumping in Bulk Acoustic Waves Resonator

TL;DR

This paper demonstrates the experimental excitation and detection of parametric spin waves in a hybrid bulk acoustic wave resonator, revealing efficient magnon pumping via acoustic waves with low power thresholds.

Contribution

It introduces a novel hybrid resonator setup combining piezoelectric, magnetic, and heavy metal layers to efficiently excite and detect magnons through acoustic pumping.

Findings

Magnons can be excited at resonator eigenfrequencies and half-value frequencies.

The system exhibits a low threshold (~0.4 mW) for magnon excitation.

Inverse spin Hall effect confirms acoustic spin pumping.

Abstract

We report on the experimental observation of excitation and detection of parametric spin waves and spin currents in the bulk acoustic wave resonator. The hybrid resonator consists of ZnO piezoelectric film, yttrium iron garnet (YIG) films on gallium gadolinium garnet substrate, and a heavy metal Pt layer. Shear bulk acoustic waves are electrically excited in the ZnO layer due to piezoeffect at the resonant frequencies of the resonator. The magnetoelastic interaction in the YIG film emerges magnons (spin waves) excitation by acoustic waves either on resonator's eigenfrequencies or the half-value frequencies at supercritical power. We investigate acoustic pumping of magnons at the half-value frequencies and acoustic spin pumping from parametric magnons, using the inverse spin Hall effect in the Pt layer. The constant electric voltage in the Pt layer, depending on the frequency, the magnetic field, and the pump power, was systematically studied. We explain the low threshold obtained (~0.4 mW) by the high efficiency of electric power transmission into the acoustic wave in the resonator.