Abstract
As a collective quasiparticle excitation of the magnetic order in magnetic materials, spin wave, or magnon when quantized, can propagate in both conducting and insulating materials. Like the manipulation of its optical counterpart, the ability to manipulate spin wave polarization is not only important but also fundamental for magnonics. With only one type of magnetic lattice, ferromagnets can only accommodate the right-handed circularly polarized spin wave modes, which leaves no freedom for polarization manipulation. In contrast, antiferromagnets, with two opposite magnetic sublattices, have both left and right-circular polarizations, and all linear and elliptical polarizations. Here we demonstrate theoretically and confirm by micromagnetic simulations that, in the presence of Dzyaloshinskii-Moriya interaction, an antiferromagnetic domain wall acts naturally as a spin wave polarizer or a spin wave retarder (waveplate). Our findings provide extremely simple yet flexible routes toward magnonic information processing by harnessing the polarization degree of freedom of spin wave.
Highlights
As a collective quasiparticle excitation of the magnetic order in magnetic materials, spin wave, or magnon when quantized, can propagate in both conducting and insulating materials
We show theoretically and confirm by micromagnetic simulations that, utilizing the Dzyaloshinskii-Moriya interaction (DMI) existing in the symmetry-broken systems[32, 33] an antiferromagnetic domain wall serves as a spin wave polarizer at low frequencies and a retarder at high frequencies
The antiferromagnetic domain wall based spin wave polarizer/ retarder mimics its optical counterpart in many aspects
Summary
As a collective quasiparticle excitation of the magnetic order in magnetic materials, spin wave, or magnon when quantized, can propagate in both conducting and insulating materials. Most magnonic devices proposed or realized so far mainly use the spin wave amplitude[13,14,15,16,17,18] or phase[19,20,21,22,23] to encode information, and spin wave polarization is rarely used except in very few cases[24]. With only one type of magnetic lattice, ferromagnets can only accommodate the right-circular polarization, there is no freedom in polarization manipulation. This situation is similar to the case of half-metal, which has only one spin spieces[25]. For photon, an array of parallel metallic wires functions as an optical polarizer[9], and a block of birefringent material with polarization-dependent refraction indices acts as an optical waveplate[31]
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