Figure 1

(a) Layer sequence used to roll up a strained ${\mathrm{Ni}}_{80}{\mathrm{Fe}}_{20}/\mathrm{GaAs}/{\mathrm{In}}_{20}{\mathrm{Ga}}_{80}\mathrm{As}$ layer system into a Permalloy microtube (RUPT). (b) Sketch of a RUPT positioned on the signal line (S) between the two ground lines (G) of a coplanar waveguide to perform microwave absorption measurements. (c) SEM image of RUPT $A$ corresponding to the scheme in (b). The inset shows 3.5 tight windings of the strained layer system in a tube cross section drilled by focused ion beams after the measurements were performed.Reuse & Permissions

Figure 2

(a) and (c) show microwave power absorption spectra at $H=0$ for RUPT $A$ and RUPT $B$, respectively. In both cases, four successive resonances corresponding to azimuthal spin-wave modes with number $n=0$, 1, 2, and 3 can be identified. (b) and (d) show the magnetic field dependence of the measured resonance frequency peaks indicated by symbols for RUPT $A$ and RUPT $B$, respectively, in very good agreement with the corresponding theory curves calculated with our spin-wave interference model ($n=0$: ■, continuous curve; $n=1$: ●, dashed curve; $n=2$: ▲, dotted curve; $n=3$: ◆, dash-dotted curve). As indicated, the magnetic field points along the tube axis.Reuse & Permissions

Figure 3

Calculated magnetic dispersion for RUPT $A$ at $H=0$ with an effective thickness $t_{\mathrm{eff}}=37\mathrm{nm}$ and an effective demagnetizing field of ${\mu }_0{H}_{\mathrm{dem}}=16\mathrm{mT}$. The dotted lines mark the wave vector for modes $n=0$, 1, 2, and 3 and the corresponding resonant frequencies. The inset color plots show the phase distribution in the RUPT for $n=0$, 1, 2, and 3 [red (light gray) and blue (gray) represent opposite phase].Reuse & Permissions

Figure 4

(a) and (b) show the hard-axis magnetic field dependence of the $n=0$ resonance frequency for RUPT $A$ and RUPT $B$, respectively. In both cases, the resonance frequency reaches a minimum, from which we can extract the absolute value of the effective demagnetizing field $H_{\mathrm{dem}}$.Reuse & Permissions