Are values of parameters describing magnetic properties of crystal really fixed?

The selected factors (e.g., deviation from stoichiometry, doping level, or free-carrier concentration) influencing the lattice parameter value of a diluted magnetic semiconductor (DMS) are discussed. Changes in the lattice parameter driven by these factors modify the superexchange interaction between the magnetic ions. It is demonstrated that in specific situations parameters describing the superexchange cannot be treated as fixed ones and effects mentioned above play a noticeable role in some materials so cannot be neglected. The cases of the well-known Zn1−xMnxTe and Ga1−xMnxAs mixed crystals are analyzed as examples.