Dynamic magnetostriction for antiferromagnets
Résumé
In this paper, we study the switching properties of the dynamics of magnetic moments that interact with an elastic medium. To do so, we construct a Hamiltonian framework that can take into account the dynamics in phase space of the variables that describe the magnetic moments in a consistent way. It is convenient to describe the magnetic moments as bilinears of anticommuting variables that are their own conjugates. However, we show how it is possible to avoid having to deal directly with the anticommuting variables themselves, only using them to deduce nontrivial constraints on the magnetoelastic couplings. We construct the appropriate Poisson bracket and a geometric integration scheme that is symplectic in the extended phase space and that allows us to study the switching properties of the magnetization, which are relevant for applications, for the case of a toy model for antiferromagnetic NiO, under external stresses. In the absence of magnetoelastic coupling, we recover the results reported in the literature and in our previous studies. In the presence of the magnetoelastic coupling, the characteristic oscillations of the mechanical system have repercussions on the Néel order parameter dynamics. This is particularly striking for the spin accumulation, which is more than doubled by the coupling to the strain; here as well, the mechanical oscillations are reflected on the magnetic dynamics. As a consequence of such a stress-induced strain, the switching time of the magnetization is slightly faster, and the amplitude of the magnetization is enhanced.