  Emergent electromagnetic induction based on electrodynamics of noncollinear
spin states may enable dramatic miniaturization of inductor elements widely
used in electric circuits, yet many issues are to be solved toward application.
One such problem is how to increase working temperature. We report the large
emergent electromagnetic induction achieved around and above room temperature
based on short-period ($\leq$ 3 nm) spin-spiral states of a metallic helimagnet
${\rm YMn}_{6}{\rm Sn}_{6}$. The observed inductance value $L$ and its sign are
observed to vary to a large extent, depending not only on the spin helix
structure controlled by temperature and magnetic field but also on the current
density. The present finding on room-temperature operation and possible sign
control of $L$ may provide a new step toward realizing microscale quantum
inductors.
