Fig. 4: Analysis of non-reciprocity.
From: Geometry-induced spin chirality in a non-chiral ferromagnet at zero field
a,b, Numerical simulation results of the remanent magnetic textures at +0 mT (a) and −0 mT (b). The tube’s colour code denotes the sign of the mz component: red (+) and blue (−). c,d, Numerical simulation results of the magnon dispersion relations on RH nickel screws at +0 mT (c) and −0 mT (d). The noisy appearance reflects the finite frequency and spatial resolution of the simulations on ACMs. Analytical calculations of the magnon dispersion of tubes with helical spin texture in the thin-shell limit are shown together with the numerical results. e, Optimization of non-reciprocity in terms of frequency asymmetry of the m = 0 mode (Δf0) by varying geometric and materials parameters and the tilting angle of the helical spins taken with respect to the longitudinal axis. f,g, Optimization of the Δf0 (f) and the m = ±1 modes (Δf1) (g) for two different materials: nickel and permalloy (Py).
