Abstract
Antiferromagnetic two-dimensional (2D) materials are currently under intensive theoretical and experimental investigations in view of their potential applications in antiferromagnet-based magnonic and spintronic devices. Recent experimental studies revealed the importance of magnetic anisotropy and of Dzyaloshinskii-Moriya interactions (DMI) on the ordered ground state and the magnetic excitations in these materials. In this work we present a robust classical field theory approach to study the effects of anisotropy and the DMI on the edge and bulk spin waves in 2D antiferromagnetic nanoribbons. We predict the existence of a new class of nonreciprocal edge spin waves, characterized by opposite polarizations in counter-propagation. These novel edge spin waves are induced by the DMI and are fundamentally different from conventional nonreciprocal spin waves for which the polarization is independent of the propagation direction. We further analyze the effects of the edge structures on the magnetic excitations for these systems. In particular, we show that anisotropic bearded edge nanoribbons act as topologically trivial magnetic insulators with potentially interesting applications in magnonics. Our results constitute an important finding for current efforts seeking to establish unconventional magnonic devices utilizing spin wave polarization.
Highlights
The polarization of a spin wave is determined by the precessing direction of the magnetization and constitutes an important additional intrinsic degree of freedom, beside the spin wave amplitude and phase
Antiferromagnetic domain walls with Dzyaloshinskii-Moriya interactions (DMI) have been proposed as spin wave polarizer, retarder and transistor[4,5]
The interaction in the 2D antiferromagnetic honeycomb nanoribbon is described by a semi-classical Heisenberg Hamiltonian expressed as follows
Summary
In the Néel antiferromagnetic ordering state, the spins on A (blue) and B (red) honeycomb sublattices are conventionally assumed to be aligned parallel and antiparallel to the z-axis. The interaction in the 2D antiferromagnetic honeycomb nanoribbon is described by a semi-classical Heisenberg Hamiltonian expressed as follows. →r = vectors of a x x + y nearest yis the position vector of a site on the neighbor and a nearest neighbor hreosnpeeycctoivmelby.laTthtiecev,etctiosrti→mS e=, →δSxaxnd+→δSy′ yarreepthreespeonstistitohne spin component in the plane of the honeycomb lattice. The parameter D determines the strength of the DMI, whereas the orientation of D in the honeycomb lattice is determined in the. The DMI between an A-site and any of its nearest neighbors can be rewritten as. With Eq 1, one can use the standard classical field theory formalism[1,2,3,11,51,52,59,60,61,62,63] to determine the effective fields
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