Frequency linewidth and decay length of spin waves in curved magnetic membranes

Abstract

The curvature of a magnetic membrane was presented as a means of inducing nonreciprocities in the spinwave (SW) dispersion relation (see [Otálora et al. Phys. Rev. Lett., 2016 117, 227203] and [Otálora et al. Phys. Rev. B., 2017 95, 184415]), thereby expanding the toolbox for controlling SWs. In this paper, we further complement this toolbox by analytically showing that the membrane curvature is also manifested in the absorption of SWs, leading to a difference in the frequency linewidth (or lifetime) of counterpropagating magnons. Herein, we studied the nanotubular case, predicting changes of approximately greater than 10% and up to 20% in the frequency linewidth of counterpropagating SWs for a wide range of nanotube radii ranging from 30 nm to 260 nm and with a thickness of 10 nm. These percentages are comparable to those that can be extracted from experiments on heavy metal/magnetic metal sandwiches, wherein linewidth asymmetry results from an interfacial Dzyaloshinskii-Moriya interaction (DMI). We also show that the interplay between the frequency linewidth and group velocity leads to asymmetries in the SW decay length, presenting changes between 10% and 22% for counterpropagating SWs in the frequency range of 2 -10 GHz. For the case of the SW dispersion relation, the predicted effects are identified as the classical dipole-dipole interaction, and the analytical expression of the frequency linewidth has the same mathematical form as in thin films with the DMI. Furthermore, we present limiting cases of a tubular geometry with negligible curvature such that our analytical model converges to the case of a planar thin film known from the literature. Our findings represent a step forward toward the realization of three-dimensional curvilinear magnonic devices.

Symmetry and curvature effects on spin waves in vortex-state hexagonal nanotubes

“…While many of the aforementioned effects have been investigated mostly in bulk or in flat thin-film samples, over the last decade, curvature-induced effects have been uncovered as a new way to manipulate magnetic equilibria and spin dynamics. Numerous analytic and numerical works have already shown that the surface curvature and geometry of 3D magnetic membranes leads to phenomena not present in flat specimens of the same material [25][26][27][28][29][30][31][32][33][34]. For example, in conventional soft magnetic materials, exotic noncollinear magnetic textures such as skyrmions [35] may be stabilized by bending the magnetic material.…”

A platform for nanomagnetism – assembled ferromagnetic and antiferromagnetic dipolar tubes

“…The experimental realization of cylindrical magnetic objects is very demanding since curvature effects might be overshadowed by wall pinning on imperfections, such as grain boundaries and edges 22 . The realization of presented quasi-one-dimensional or edge free ferromagnets and antiferromagnets would create an accessible platform for testing concepts of spin-based electronics (e.g., Cherenkov-like spin wave emission 23,71 or curvature induced non-reciprocities in magnonics 26,72 ) and information technologies by getting around a requirement of robust magnetic uniformity at temperatures of technological relevance. An additional application of the tubular assemblies of dipoles could be modeling of the ordered planar systems due to the absence of the lateral edges in curved geometry and low energy barriers.…”

Advances in Magnetics Roadmap on Spin-Wave Computing

“…On the other hand, overgrowth provides a reliable approach to create curved magnetic nanodevices with particularly the tubular topology. The latter one owns a special potential considering recent theoretical progress that links the curvature of magnetic elements to magnetochiral spin-wave properties [213], [214], [215].…”

“…On the one hand, such a nanotube represents a prototypical element which serves as a vertical magnonic interconnect in a 3D network. On the other hand, its magnetochiral properties [213], [214], [215] enable spin-wave transport with tailored nonreciprocity in oscillation frequency, amplitude, group velocity, and decay length [221]. The mean nanotube curvature renormalizes the dipolar and isotropic exchange interaction in such a way that, depending on the equilibrium magnetic state, the nonreciprocity is controllable on-demand for applications [221].…”