Electrically induced strong modulation of magnon transport in ultrathin magnetic insulator films

Magnon transport through a magnetic insulator can be controlled by current-biased heavy-metal gates that modulate the magnon conductivity via the magnon density. Here, we report nonlinear modulation effects in $10\phantom{\rule{0.16em}{0ex}}\mathrm{nm}$ thick yttrium iron garnet (YIG) films. The modulation efficiency is larger than 40%/mA. The spin-transport signal at high dc current density $(2.2\ifmmode\times\else\texttimes\fi{}{10}¹¹\phantom{\rule{0.16em}{0ex}}\mathrm{A}/{\mathrm{m}}²)$ saturates for a $400\phantom{\rule{0.16em}{0ex}}\mathrm{nm}$ wide Pt gate, which indicates that even at high current levels a magnetic instability cannot be reached in spite of the high magnetic quality of the films.