  The present work reproduces the room temperature ferromagnetism by doping
magnetic Mn atoms in diamagnetic ZnO. The ferromagnetic ordering is extended up
to 640 K in mechanical milled Zn0.95Mn0.05O samples. The bulk and
nanocrystalline samples are stabilized in hexagonal crystal structure with
space group p63mc. The grain size and lattice strain of the samples, estimated
from XRD spectrum using Williamson-Hall plot, showed a significant variation
with milling time. Surface structure (morphology, distribution of grains and
elements) is observed to be reasonably good from SEM picture and EDX spectrum
at room temperature. The ferromagnetic ordering in bulk, milled and alloyed
samples is primarily due to the diffusion of Mn(2+) ions into the lattice sites
of ZnO. The enhancement of magnetic moment and ferromagnetic ordering
temperature with reducing the grain size is discussed in terms of the existing
theoretical predictions and experimental works. The role of mechanical milling
induced disorder for the enhancement of room temperature ferromagnetism in
Zn0.95Mn0.05O (dilute magnetic semiconductor) is also highlighted.
