  The study of structural, electronic, magnetic, and elastic properties of new
series of semi-Heusler alloys MnNbZ (Z=As, Sb) and FeNbZ (Z=Sn, Pb) has been
performed by density functional theory. The magnetic phase and hence the
structural stability of the alloys were considered wherein ferromagnetic state
is found to stable. The half-metallic states are observed from the density of
states and band structure calculations. The total magnetic moments found for
all studied compounds are 1 $\mu_B$/f.u., which obey Slating-Pauling rule for
semi-Heusler with ferromagnetic behavior. The calculated elastic constant
C$_{ij}$, cohesive energy, and formation energy confirmed that these materials
are mechanically stable. Among the four system, MnNbAs is found to have the
highest ductility while the remaining systems are found to be brittle in
nature. These properties confirmed that among others, MnNbAs is one of the
novel candidate for spintronic devices applications.
