  Experimental observations of vacuum radiation and vacuum frictional torque
are challenging due to their vanishingly small effects in practical systems.
For example, a rotating nanosphere in free space slows down due to friction
from vacuum fluctuations with a stopping time around the age of the universe.
Here, we show that a spinning yttrium iron garnet (YIG) nanosphere near
aluminum or YIG slabs exhibits vacuum radiation eight orders of magnitude
larger than other metallic or dielectric spinning nanospheres. We achieve this
giant enhancement by exploiting the large near-field magnetic local density of
states in YIG systems, which occurs in the low-frequency GHz regime comparable
to the rotation frequency. Furthermore, we propose a realistic experimental
setup for observing the effects of this large vacuum radiation and frictional
torque under experimentally accessible conditions.
