Extraordinary Hall effect in La_(0.7)Ca_(0.3)MnO_3 and La_(0.7)Ba_(0.3)MnO_3 thin films

摘要

The Hall effect of La_(0.7)Ca_(0.3)MnO_3 and La_(0.7)Ba_(0.3)MnO_3 thin films was measured in magnetic fields #mu#_0H <= 1 T and for temperatures 10 K <= T <= 340 K. In the ferromagnetic phase the slope of the Hall resistivity at zero magnetic induction rapidly increases with temperature 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.