Extraordinary Hall effect in ${\mathrm{SrRuO}}_3$

We have measured the Hall effect in thin films of the itinerant ferromagnet ${\mathrm{SrRuO}}_3$ as a function of temperature $(1.8\mathrm{}\mathrm{K}–300\mathrm{K})$ and field $(0\mathrm{}–8\mathrm{T}).\mathrm{}$ We find that the extraordinary Hall coefficient $R_s$ changes sign and can be described as $R_s\approx {\mathrm{cT}}^5+b{\rho }^2$ where T is temperature and $\rho$ is resistivity. We discuss possible interpretations of this result.