Extending the Magnetic Deformation Proxy to Disordered Systems

Identifying better magnetocaloric materials is a necessary step in the advancement of magnetic refrigeration technology. The material property which distinguishes a promising candidate is a large entropy change upon isothermal application of a magnetic field (ΔS_M). The magnetic deformation, Σ_M, is a computational proxy which compares the relaxed structures of a composition with and without spin polarization included in the density functional theory (DFT) framework, and it has been shown to correlate well with experimental magnetic entropy changes. In this study, we extend the magnetic deformation proxy to systems which have a degree of configurational disorder which cannot be encapsulated computationally by a single unit cell. Through generation of supercells, we scan relevant ranges of x for the known magnetocalorics MnFe_1-xCo_xGe and (MnCoGe)_1-x(NiCoGe)_x. We show that trends of Σ_M vs. x match well with experimentally determined ΔS_M vs. x and suggest how to apply the computational proxy to other disordered systems.