  Room temperature ferromagnetism has been one of the most sought after topics
in today's emerging field of spintronics. It is strongly believed that defect-
and inhomogeneity- free sample growth should be the optimal route for achieving
room-temperature ferromagnetism and huge efforts are made in order to grow
samples as "clean" as possible. However, until now, in the dilute regime it has
been difficult to obtain Curie temperatures larger than that measured in well
annealed samples of (Ga,Mn)As ($\sim$190 K for 12% doping). In the present
work, we propose an innovative path to room-temperature ferromagnetism in
diluted magnetic semiconductors. We theoretically show that even a very small
concentration of nanoscale inhomogeneities can lead to a tremendous boost of
the critical temperatures: up to a 1600% increase compared to the homogeneous
case. In addition to a very detailed analysis, we also give a plausible
explanation for the wide variation of the critical temperatures observed in
(Ga,Mn)N and provide a better understanding of the likely origin of very high
Curie temperatures measured occasionally in some cases. The colossal increase
of the ordering temperatures by nanoscale cluster inclusions should open up a
new direction toward the synthesis of materials relevant for spintronic
functionalities.
