Fig. 2: Reprogrammable non-reciprocal magnons of an ACM in the remanent state.
From: Geometry-induced spin chirality in a non-chiral ferromagnet at zero field
a, Sketch of μBLS spectroscopy performed on an ACM. b, The different light scattering geometries at positions z < 0 µm and z > 0 µm lead to differently transferred magnon wavevectors as sketched for the Stokes signal. c, Magnon spectra obtained on a RH ACM in the remanent state +0 mT (after applying +30 mT) at position z = −0.7 µm. d, Intensity non-reciprocity η at 10 GHz evaluated at position z = −0.7 µm as a function of magnetic field and sweep direction (indicated by red and blue arrows) shows a hysteretic behaviour. Error bars represent the s.d. obtained from averaging over three consecutive measurements at each field point. e, Non-reciprocity parameter η extracted from spectra taken at µ0H = ±0 mT after applying a magnetic field of ±30 mT along axial directions of a RH ACM. η was measured at f = 10 GHz five consecutive times with the same polarity (cycles) at position z = −0.7 µm before reversing the magnetic field history. The data reflect the robust programmability of signal asymmetry (amplitude non-reciprocity) at zero field. f, Numerically computed toroidal moment τ of a RH ACM simulated as a function of field H and its sweep direction. The field was applied along the z direction and swept from negative to positive (blue lines) and back (red lines). The hysteretic behaviour leads to a reprogrammable τ of opposite sign at µ0H = 0 mT.
