Figure 1

(a) Optically induced magnetic oscillations for 80% Co. The vertical dotted line indicates zero delay between pump and probe pulses and the solid curve is a fit using Eq. (7). The experiment schematic and the fast Fourier transform (FFT) spectrum of the oscillations are shown as insets. (b) Oscillation frequencies for 79.5% Co, as a function of the external magnetic field applied at $\approx 55°$ from the sample normal. The dash-dotted line is a fit using Eq. (4). (c)–(d) Oscillation frequencies as a function of cobalt concentration (symbols). Solid lines are guides to the eye. (e)–(f) Schematics that show the precession of the magnetizations around (e) the effective field ${\mathbf{H}}_{\mathrm{eff}}$ and (f) the exchange fields ${\mathbf{H}}_{\mathrm{exch}}^{\mathrm{Co},\mathrm{Gd}}$, which give rise to the FMR and exchange modes, respectively.Reuse & Permissions

Figure 2

(a) Magnetic oscillations corresponding to the FMR mode for 78% Co as a function of pump-laser fluence. The solid curves are fits using function $y_1$ [Eq. (7)], and the dash-dotted line is a guide to the eye that shows the evolution of the FMR mode’s period. Frequencies of the FMR and exchange modes as a function of pump-laser fluence are shown as inset. (b) Resonance amplitudes of the two modes as a function of pump-laser fluence.Reuse & Permissions