Fig. 3: Dependence of the magnon population on magnetic field.
a Map of the BLS intensity as a function of f and μ0H. The two pairs of dashed lines mark the spectral ranges used for integration in (b) and (c). The thin dotted line marks the line cut shown in Fig. 2d. b, c BLS intensity integrated within the two bounds marked by the dashed lines in (a), corresponding to the occupancy of the n = 0 mode (b) and the n = 1 mode (c). The dotted vertical lines identify the mode order/(see d–f). The orange and teal shaded regions mark the range of enhanced BLS contrast. d Schematic cut through the sample. When applying a current in Pt, magnons are confined below the central wire due to the nonlinear frequency shift (purple shading). Consequently, standing wave patterns (black lines) emerge. The vertical mode profile of the lowest two magnon branches is depicted by the orange (n = 0) and teal (n = 1) lines on the right. e Calculated dispersion of the two lowest magnon branches shows that the wave vector \({k}_{\min }\) of the band minimum shifts with magnetic field. f Position \({k}_{\min }\) as a function of magnetic field. Constructive interference occurs when kmin,n = (l + 1)π/w (see d). The vertical dotted lines correspond to the two magnetic fields shown in (e). g BLS signal integrated under the n = 0 peak recorded while scanning the laser spot across the injector wire (gray shaded region). The trace has been normalized to its maximum value. All data in the figure were recorded at a dc current of Idc = −1 mA and with the magnetic field applied at α = 270°.
