  The ferromagnetic Heusler alloy $Ni_2MnGa$ had been of major interest in the
past few years because of its magnetic properties which can be easily tuned.
The $Ni_2MnGa$ Heusler alloys are intermetallic alloy with $L2_1$ structure.
Here we report a detailed investigation of the effect of doping of Co and Mn in
Ni2MnGa. Magnetic properties and electronic structure of
$Ni_{2-x}Co_xMnGa_{1-y}Mn_y$ Heusler alloys have been studied by using Green's
function-based KKR-CPA method based DFT calculations. We will show the
magnetization can be tuned depending on the Co and Mn occumencies. We will also
discuss the critical temperature, magnetic interactions and magnetic stability
of the systems.
