Extraordinary Hall effect in CoxPt100−x films

${\mathrm{Co}}_x{\mathrm{Pt}}_{\text{100−x}}$ alloy films, $\text{8.7⩽x⩽40.6,}$ have been fabricated by the magnetron co-sputtering technique. The structure of the films has been studied by x-ray diffraction and transmission electron microscopy. The results indicate the existence of ${\mathrm{CoPt}}_3$ phase in these films. Electric transport and magnetotransport measurements have been performed in the temperature range of 5–300 K and field range of −5–5 T, in which the longitudinal resistivity ${\mathrm{(\rho }}_{\mathrm{xx}})$ and extraordinary Hall resistivity ${\mathrm{(\rho }}_s)$ have been obtained. A power law dependence of extraordinary Hall resistivity on the longitudinal resistivity, ${\rho }_s{\mathrm{\propto \rho }}_{\mathrm{xx}}^v,$ is observed, however the value of the exponent $\mathrm{(v)}$ changes from 1 to 1.6 as the temperature changes from 5 to 100 K and above. Different $v$ values suggest different mechanisms of the extraordinary Hall effect. The dependence of the Hall resistivity on the Co concentration, x, has also been studied.