Unified generalized universal equation of states for magnetic Co, Cr, Fe, Mn and Ni: an approach for non-collinear atomistic modelling

Abstract Despite great efforts to study magnetic properties of 3d-transition metals from both fundamental and applied interest, there exists no modelling approach that would be able to describe magnetic and structural phase stability of all these elements on a unified formalism. In this work, we propose a qualitative improvement of the Generalisation of the Universal Equation of States (GUES) that we presented recently in a previous work developed and tested for cubic structures in Fe. The GUES is now extended to other 3d-transition magnetic elements and crystal lattices, where now magnetic Co, Cr, Mn, and Ni are considered, including both cubic and hexagonal structures, and also covering ferromagnetic (FM) and antiferromagnetic (AFM) configurations. An extensive database has been developed and used to fit all parameters and functions for all considered elements. The current GUES unifies the two previous separate approaches for FM and AFM configurations, allowing for non-collinear calculations, which are tested for Co, Cr, Fe, Mn and Ni. The approach is consistent with the Stoner model of band magnetism and the Ginzburg-Landau approximation used in the magnetic cluster expansion method, as well as with non-collinear magnetism described in the Heisenberg-Landau Hamiltonians. Importantly, it also includes magneto-volume effects, which are important for understanding defect properties in magnetic materials. This work permits considering the development of a new class of magnetic interatomic potentials for non-collinear simulations based on the approach proposed by the GUES. (The figures shown in this article can be seen in colour only in the electronic version).