  The focus of our work is on the production of highly magnetic materials out
of Cu clusters. We have studied the relative effects of N-capping as well as N
mono-doping on the structural stability and electronic properties of the small
Cu clusters using first principles density functional theory based electronic
structure calculations.
  We find that the N-capped clusters are more promising in producing giant
magnetic moments, such as 14 $\mu_B$ for the Cu$_6$N$_6$ cluster and 29 $\mu_B$
for the icosahedral Cu$_{13}$N$_{12}$ clusters. This is accompanied by a
substantial enhancement in their stability. We suggest that these giant
magnetic moments of the capped Cu$_n$ clusters have relevance to the observed
room temperature ferromagnetism of Cu doped GaN. For cage-like hollow
Cu-clusters, an endohedral Cr-doping together with the N-capping appears as the
most promising means to produce stable giant magnetic moments in the copper
clusters.
