  We study the diffusive transport of magnons through the compensated
ferrimagnetic insulator Gd3Fe5O12 (GdIG). The magnons are injected and detected
electrically in a non-local measurement configuration via two parallel Pt
strips deposited on top of the ferrimagnet. GdIG exhibits a rich magnon
spectrum, with several thermally populated magnon bands at room temperature. We
observe a strong temperature and field dependence of the non-local voltage in
the detector strip. Just below the magnetization compensation temperature we
find that the increasing magnetic field causes an unexpected enhancement of the
non-local signal. A comparison with GdIG spin wave spectra obtained from
atomistic modeling indicates that the thermal magnon population is important
for understanding the non-local voltage signal.

Mesoscale and Nanoscale Physics