Frustrated magnetism in superconducting hexagonal Fe: Calculation of inter-atomic pair exchange interactions

Abstract

We calculate magnetic exchange interaction parameters in hcp Fe using magnetic force theorem in density functional theory in a range of volumes, which covers the region of stability of the superconducting state. The calculations are done for a paramagnetic state using disordered local moment model within a local fixed spin-moment constraint. It is found that exchange interaction parameters strongly favor antiferromagnetic inter-plane stacking of the basal hcp planes. At the same time, the nearest neighbor in-plane exchange interaction parameters are also strongly antiferromagnetic, which should lead to magnetic frustrations in the planar triangular lattice. Eventual consequences of the magnetic frustration effects on the interplay between magnetism and superconductivity in hcp Fe under pressure are discussed.