Figure 1: (Top) Energy level diagram describing the stabilization of the ferromagnetic spin arrangement as a result of the interaction between two hybrid orbitals located on two impurities, here labeled ${\text{TM}}_1$ and ${\text{TM}}_2$, in a tetrahedral semiconductor. In the case of partial occupancy of the individual hybrid orbitals, the ferromagnetic configuration is stabilized by the preferential filling of the lower energy state. (Bottom) Energy level diagram describing how an individual hybrid orbital is formed from the coupling between the host cation vacancy orbitals t(p) and the $3d$ orbitals t(d)+e(d). See Ref. [16].