  We have used low energy implanted muons as a volume sensitive probe of the
magnetic properties of EuO_{1-x} thin films. We find that static and
homogeneous magnetic order persists up to the elevated T_C in the doped samples
and the muon signal displays the double dome feature also observed in the
sample magnetization. Our results appear incompatible with either the magnetic
phase separation or bound magnetic polaron descriptions previously suggested to
explain the elevated T_C, but are compatible with an RKKY-like interaction
mediating magnetic interactions above 69 K.
