Time-resolved Kerr effect in SrRuO$_3$: observation of oscillatory dynamics

We report measurements of magnetization dynamics in thin films of the perovskite transition metal oxide SrRuO$_3$, a metallic compound that is ferromagnetic below approximately 150 K. The dynamics of the magnetization vector, \overrightarrow{M}, were measured using the time-resolved magneto-optic Kerr effect. In this technique a pump laser pulse, at photon energy 1.5 eV, perturbs the magnet by reducing the magnitude of \overrightarrow{M} and changing the direction of the anisotropy field. The subsequent dynamics of \overrightarrow{M} are measured by detecting the rotation of the plane of polarization of a time-delayed probe beam that is reflected from the surface of the sample. Below $\sim$ 100 K, we observe a damped oscillation in the Kerr rotation with frequency 250 GHz. The damping decreases with decreasing temperature down to $\sim$ 50 K and remains constant below this temperature. We tentatively identify this oscillation as the \textit{q}=0 magnon, or ferromagnetic resonance frequency (FMR), of SrRuO3. The rather large value of the FMR frequency is consistent with the known large magnetocrystalline anisotropy of this compound. We will report measurements of \overrightarrow{M}(t) as a function of film thickness, residual resistance, and orientation of crystalline axes.