Formation of Co Moment in the Paramagnetic Phase of RCo2

The formation of Co magnetic moment in the paramagnetic phase of GdCo₂ has been studied by means of first principles calculations. The introduction of impurities in the transition metal-rare-earth Laves phases leads to changes in the density of states of the transition metal 3d band. In this paper, we calculate the electronic structure of GdCo2 system (a C15 unit cell) with an interstitial impurity (Ti). Calculations show that local disorder introduced by the impurity shifts the Fermi level in such a way that Co 3d up and down states split. This result suggests that local disorder may be responsible for the formation of Co moment in this system. To deepen this phenomenon, we have considered the antisite substitution of a Gd atom by a Co within the unit cell, which is the most common defect in the Laves phases. Calculations show the formation of magnetic moment in the Co atom at the substituted site as well as in their nearest Co atoms, similarly to the observed in the systems with the interstitial impurity. Our results are compatible with the reported x-ray magnetic circular dichroism measurements performed in the RCo₂ family of compounds.