Localized magnetic moments in a Dirac semimetal as a spin model with long--range interactions

We connect between the problem of thermodynamics of localized magnetic moments in a Dirac semimetal, the interaction with relativistic electrons leading to the effective ferromagnetic exchange between the moments, and the existing theories dealing with long--range exchange interaction. We point out that the results of high--temperature expansion for the free energy of a dilute ensemble of magnetic impurities in the semimetal performed by V. Cheianov et al. (Phys. Rev. B {\bf 86}, 054424 (2012)) give an indication to the existence of a new disordered fixed point in such model.