Abstract
We study theoretically spin dynamics in three-dimensional antiferromagnetic insulators with spin-orbit coupling. We focus on the antiferromagnetic insulators whose low-energy effective model possesses a topological term called the θ term. By solving the Landau-Lifshitz-Gilbert equation in the presence of the θ term, we show that the antiferromagnetic resonance can be realized by ac electric fields along with static magnetic fields. The antiferromagnetic resonance can be detected via the spin pumping from the Néel field and net magnetization. We calculate both contributions to the pumped spin current, and find that the magnitude of the ac electric field to cause the resonance state is very small (∼ 1 V/m). This indicates that spin currents can be generated efficiently. The mechanism of the antiferromagnetic resonance in this study is understood as the inverse process of the dynamical chiral magnetic effect.
Highlights
Antiferromagnets have attracted great attention recently in the field of spintronics, as a new class of materials that could be alternatives to ferromagnets.1 Microscopic magnetic moments on each atomic site cancel each other out in antiferromagnets, which results in macroscopic zero net magnetization
By solving the Landau-Lifshitz-Gilbert equation, we have shown that the AF resonance state can be realized by ac electric fields along with static magnetic fields in 3D AF
The θ term enables the coupling between the Neel field and external electric fields
Summary
Antiferromagnets have attracted great attention recently in the field of spintronics, as a new class of materials that could be alternatives to ferromagnets. Microscopic magnetic moments on each atomic site cancel each other out in antiferromagnets, which results in macroscopic zero net magnetization. Due to zero net magnetization, antiferromagnets do not generate unwanted stray fields, and are expected to be robust against (i.e., insensitive to) magnetic-field perturbation compared to ferromagnets. The spin-transfer torque, which enables the coupling between magnetization and electric current, has been utilized widely. We demonstrate that, in contrast to usual methods utilizing ac magnetic fields, the antiferromagnetic (AF) resonance can be realized by ac electric fields in a class of three-dimensional (3D) AF insulators with spin-orbit coupling. The antiferromagnetic resonance can be detected via the spin pumping from the Neel field and net magnetization. We calculate both contributions to the pumped aPresent address: Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA. We argue that the mechanism of the electric-field-induced AF resonance in this study is understood as the inverse process of a recently proposed dynamical magnetoelectric phenomenon, the dynamical chiral magnetic effect.
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