Extraordinary Hall effect in Co _xPt _100-x films

Co _xPt _100-x alloy films, 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 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 (ρ _xx) and extraordinary Hall resistivity (ρ _s) have been obtained. A power law dependence of extraordinary Hall resistivity on the longitudinal resistivity, ρ _s∝ρ _xx ^v, is observed, however the value of the exponent (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.