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In recent years, there has been growing interest in harnessing noncollinear antiferromagnets (NCAFMs) for applications in antiferromagnetic spintronics. A key requirement for their practical use is the ability to control the spin order in a reliable and tunable manner. In our recent article published in Physical Review B, we investigate how the spin order in kagome antiferromagnets—an important class of NCAFMs—can be manipulated via strain. Starting from a microscopic spin Hamiltonian, we derive an effective action for the kagome antiferromagnet that captures the coupling between the spin order and the system’s strain tensor. At the microscopic level, this coupling arises from strain-induced modifications of the Dzyaloshinskii-Moriya and exchange interactions. Using this effective description, we explore two strain-driven phenomena: (1) strain-induced switching of the antiferromagnetic spin order and (2) the piezomagnetic response. We numerically show that strain facilitates thermally assisted switching between spin configurations of opposite chirality. Specifically, we find that uniform tensile and compressive strain govern both the average switching time and the preferred switching direction between chiral states. Furthermore, we demonstrate that strain induces a net magnetization and provide an experimentally testable prediction of this effect for a typical NCAFM. Our results provide a theoretical framework for modeling strain-induced manipulation of kagome antiferromagnets, underscoring strain as a promising route for functional control of NCAFMs.

At JEMS 2025, Feodor S. Konomaev will give a talk on how the spin Seebeck effect can be enhanced by topological magnons. Mithuss Tharmalingam will present a poster on strain-induced manipulation of kagome antiferromagnets. Further details about the conference and its scientific program can be found [here].

Kjetil M. D. Hals delivered an invited talk at the QuSpin International Conference on Quantum Spintronics. Mithuss Tharmalingam and Feodor S. Konomaev presented their research in poster sessions. Further details about the conference can be found [here].

Topological magnons emerge as topologically protected spin wave states at the edges of magnets. In our recent work published in Physical Review B, we theoretically explore how these surface states can be harnessed to amplify the spin Seebeck effect (SSE) in antiferromagnets (AFMs) interfaced with normal metals (NMs). Based on a microscopic model of a kagome AFM, we demonstrate that broken mirror symmetry, combined with the Dzyaloshinskii-Moriya interaction (DMI), drives the system into a topological phase hosting spin-polarized magnons at the boundaries. Notably, linear response calculations reveal that in AFM/NM heterostructures, the topological magnons exhibit strong coupling to the metal’s charge carriers, resulting in a substantial enhancement of the SSE. The relative contribution of the topological magnons is found to be 4-5 times greater than that of the trivial magnon bands. Moreover, our results show that this enhancement is highly sensitive to the strength of the DMI.

Figure: A heterostructure composed of a kagome AFM interfaced with an NM. Topological magnons, localized at the edge of the AFM, strongly couple to the charge carriers of the NM, resulting in an enhancement of the thermally driven spin current pumped into the NM. The green arrows represent the DMI vectors along the various bonds.

The terahertz (THz) technology gap refers to a frequency range within the electromagnetic radiation spectrum where existing technologies struggle to generate and detect radiation efficiently. In a recent Physical Review Letters article, we demonstrated that certain antiferromagnetic materials manifest unique auto-oscillations – self-sustained oscillations that emerge without needing a periodic external stimulus. Even more intriguing, these auto-oscillations can be precisely controlled through electrical means across an extraordinarily broad frequency spectrum, spanning from 0 Hz to THz frequencies. These electrically controlled self-oscillations facilitate a highly efficient transformation of direct currents into THz alternating currents, which, in turn, can be harnessed to generate THz electromagnetic radiation. The underlying Kagome lattice structure, an inherent feature of a specific subset of noncollinear antiferromagnets, plays a pivotal role in our prediction. This lattice structure gives rise to two distinct ground states, each characterized by its unique chirality. We show that the correct chirality of the ground state represents the key element for achieving the predicted high-bandwidth auto-oscillations. Consequently, our findings shed light on the remarkable potential of noncollinear antiferromagnets in providing exceptional THz functional components, representing a significant stride toward bridging the current THz technology gap.