Propensity of spin fluctuations in disordered NiCoCr alloys: A first principles study

A quantum critical behavior is reported in equi-atomic NiCoCr alloy, where the ferromagnetic transition temperature goes to zero. We perform a systematic study of (NiCo)(1-x)Cr-x alloys; 0 <= x <= 1/3, by means of density functional theory based Green's function method, to understand the changes in the electronic structure and magnetic properties of this equi-atomic ternary alloy as a function of Cr at%. Chemical disorder is modeled by means of coherent-potential. approximation. To determine the propensity of spin fluctuations, we adopt to the fixed-spin moment method. A fit to the phenomenological Ginzburg Landau equation and estimation of the second derivative of the total energy with respect to magnetization shows that (NiCo)(1-x)Cr-x alloys display an increasing propensity of longitudinal spin fluctuations, proportional to the Cr at% in these alloys. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

A quantum critical behavior was observed in equi-atomic NiCoCr alloy, with the ferromagnetic transition temperature approaching zero. Using density functional theory based Green's function method and coherent-potential approximation to model chemical disorder, it was found that (NiCo)(1-x)Cr-x alloys exhibit an increasing propensity of longitudinal spin fluctuations.