Modeling Dzyaloshinskii-Moriya Interaction at Transition Metal Interfaces: Constrained Moment versus Generalized Bloch Theorem

TL;DR

This paper compares two first-principles methods for modeling Dzyaloshinskii-Moriya interaction at transition metal interfaces, highlighting their differences and applicability based on the nature of magnetism.

Contribution

It demonstrates that the generalized Bloch theorem approach is more suitable for delocalized magnetic systems, while the constrained moment method suits localized magnets.

Findings

Both methods yield similar total DMI energy.

DMI dependence on spin spiral wavelength differs significantly.

Long-range magnetic interactions influence the discrepancy.

Abstract

Dzyaloshinskii-Moriya interaction (DMI) at Pt/Co interfaces is investigated theoretically using two different first principles methods. The first one uses the constrained moment method to build a spin spiral in real space, while the second method uses the generalized Bloch theorem approach to construct a spin spiral in reciprocal space. We show that although the two methods produce an overall similar total DMI energy, the dependence of DMI as a function of the spin spiral wavelength is dramatically different. We suggest that long-range magnetic interactions, that determine itinerant magnetism in transition metals, are responsible for this discrepancy. We conclude that the generalized Bloch theorem approach is more adapted to model DMI in transition metal systems, where magnetism is delocalized, while the constrained moment approach is mostly applicable to weak or insulating magnets, where magnetism is localized.