What are the other reasons of doping a non magnetic atom in a magnetic parent compound other than seeing the changes in magnetic transitions?
In addition to the consequence mentioned by Sergei Sergeenkov, many properties can be changed by non-magnetic doping (optical, structural). But from the magnetic point of view, you may want to test how the saturation magnetization depends on doping; or the magnetocrystalline anisotropy. From a more microscopic side, local probe techniques (like PACS or Mossbauer spectroscopy) could tell you about the hyperfine interactions at the substitution crystalline site.
Hope this helps.
Non-magnetic dopant in a magnetic lattice will try to alter its magnetic interactions. As a consequence its magnetic transitions may change. As wisely said by G. F. Goya saturation magnetization and magnetic anisotropy will depend on the amount of non-magnetic dopant in a magnetic substance.