Electrically-gated laser-induced spin dynamics in magneto-electric iron garnet at room temperature

Abstract

Ultrafast pump-probe imaging reveals that the efficiency of optical excitation of coherent spins waves in epitaxial iron garnet films can be effectively controlled by an external electric field at room temperature. Although a femtosecond laser pulse alone does not excite any pronounced coherent spin oscillations, an electrical gating with the field of 0.5 MV/m dramatically changes the outcome in a laser-induced launching of spin waves. The effect, demonstrated under room-temperature conditions, is estimated to be orders of magnitude larger than in magnetic van der Waals semiconductors observed at 10 K. This electrical gating of laser-induced spin dynamics enriches opto-magnonics with a new tool and thus opens up a new avenue in fundamental and applied magnonics research.

Figures (6)

• Figure 1: Magneto-optical measurements of the Faraday rotation angle $\psi$ of the probe showing the hysteresis loop without (black curve) and with the applied electric field (orange curve). Top left: scheme of the experiment. Bottom right: the maximum amplitude of the $\psi$ angle as a function of the applied electric field. Dots show the experimentally measured maximum static Faraday rotation; the solid curve shows the calculated normal component of the equilibrium magnetization $m_z$ at $t < 0$ (see details in the text).
• Figure 2: (a, b) Time-resolved magneto-optical images of electrically-controlled laser-induced spin dynamics. The images were captured at different times without (a) and with (b) an applied electric field. A magnetic field of ${B} = 30 \, \text{mT}$ was applied in all experiments. The laser fluence was $36 \, \text{mJ/cm}^2$.
• Figure 3: Magnetization dynamics extracted from the time-resolved magneto-optical images without (black) and with applied electric field $E=0.5$ MV/m (orange). A magnetic field $B = 30$ mT was applied in the plane of the sample. The laser fluence was 36 mJ/cm$^2$. The two sets of traces are offset relative to each other for convenience.
• Figure 4: Calculated dynamics of the out-of-plane component of the magnetization $m_z$ with and without applied electric field. The dynamics is triggered as a result of ultrafast heating leading to different dynamics of magneto-crystalline anisotropy and magnetization as explained in Ref.gareev2025strongly.
• Figure A1: Calculated distribution of the electric field at applied voltage $U_{DC} = 500$ V. The inset shows zoom in of the pumped BiLu:IG part. Vertical purple lines indicate the pump beam.