Anomalous Hall effect of Nd_0.7Sr_0.3MnO₃ films with large magnetoresistance ratio: Evidence of Berry phase effect

The transverse Hall resistivity, ρ_xy, and magnetization, M, of [110] and [100] oriented epitaxial Nd_0.7Sr_0.3MnO₃ films with large magnetoresistance were measured as a function of temperature and applied magnetic field to study the ordinary and spontaneous Hall coefficients. In the ferromagnetic regime, 100 K <T<200 K, (-R_s/R_o)×T was found to be proportional to exp(-E_c/k_BT), where R_s is the spontaneous Hall coefficient, R_o is the ordinary Hall coefficient, and E_c is the core energy of the magnetic dipole. In addition, R_s was found to be proportional to ρ_xx² in the low-temperature regime (T<160 K) where the ordinary Hall coefficient, R_o, is independent of temperature. A scaling behavior, R_s∝ρ_xx was observed at high temperatures (T>160 K). Hall effects of [110] and [100] oriented films are compared to each other. The results are discussed in terms of the exiting theories.