Micromagnetic and analytical descriptions of antiferromagnets

The study of antiferromagnets (AFMs) [1] is growing due to the potential applications ranging from sensors, memories, etc [2-4]. When these materials are driven out of equilibrium, their dynamic is governed by the large exchange interaction that governs the antiferromagnetic order. This exchange interaction is the main ingredient that gives rise to resonance in the range of THz [5], making AFMs promising for the development of THz spintronics. A full micromagnetic framework (µMag) for the simulations of AFMs has been developed. Modeling of AFMs is performed by considering two different sublattices [4]. The temporal evolution of these two sublattices is assumed to be described by two Landau-Lifshitz-Gilbert (LLG) equations, augmented with a Slonczewski-like torque [6]. Those two equations, however, are coupled through the exchange field which accounts for the exchange contributions due to both, intra-sublattice and inter-sublattice neighbors [3]. Here we develop a one dimensional model (1DM) in a similar way as in ferromagnets [7] to describe domain walls in AFMs. The results depicted by such a model are compared with the full µMag simulations, showing a rather good agreement, as can be checked in Figure 1. Besides, the proposed model will be compared with a previous one based on the temporal evolution of the Nèel order parameter [8]. Finally, we perform a systematic study on the effect of the three exchange constants under play, the intra-sublattice, the homogeneous inter-sublattice and the inhomogeneous inter-sublattice constants. This analysis shows that domain wall velocity does not depend on the homogeneous inter-sublattice exchange but it depends on both, intra- and inter-sublattice inhomogeneous exchanges, due to the domain wall width dependence on these parameters, ( ) ( )