Extraordinary Hall effect in La0.7Ca0.3MnO3 and La0.7Ba0.3MnO3 thin films

The Hall effect of La0.7Bn0.3MnO3 and La0.7Ca0.3MnO3 thin films was measured in magnetic fields mu(0)H less than or equal to 1 T and for temperatures 10 K less than or equal to T less than or equal to 340 K. In the ferromagnetic phase the slope of the Hall resistivity at zero magnetic induction rapidly increases with tempera ture until a maximum is reached at the Curie temperature T-C. A detailed comparison of the Hall resistivity with the magnetization facilitates the separation of the ordinary and extraordinary Hall effect. The ordinary Hall constant R-H shows a jump below T-C. The extraordinary Hall constant R-A scales with the zero-field resistivity. At low temperatures we find a quadratic dependence of R-A on the resistivity crossing over to a linear dependence at higher temperatures. Whereas the quadratic scaling law in the ferromagnetic phase can be explained by a conventional side-jump mechanism, the linear dependence near T-C and in the hopping regime is inconsistent with conventional skew scattering. The data are compared to a recent theory of the Hall effect in double-exchange ferromagnets.