Electrical Transport Properties of Single Crystal Sr3Ru2O7: The Possible Existence of an Antiferromagnetic Instability at Low Temperatures

We report the results of Hall coefficient R_H and magnetoresistance (MR) measurements on single crystalline samples of Sr3Ru2O7 grown by the floating zone method. R_H was found to be positive over the entire temperature range studied (0.3 - 300K). Its temperature (T) dependence follows closely that of the magnetic susceptibility, including a maximum at a characteristic temperature T=17 K. We show that R_H can be decomposed into normal and anomalous parts as in the case of skew scattering in heavy-fermion compounds and ferromagnetic metals. This, together with the observation that the longitudinal MR is greater than the transverse MR at the same magnetic field and temperature, suggests that magnetic fluctuations dominate the electrical transport properties in Sr3Ru2O7. We found a crossover in the sign of the MR at T*, from positive to negative as the temperature increased, for both the transverse and the longitudinal configurations. In addition, a non-monotonic behavior in the field dependence of the MR was found at low temperatures. These observations suggest that the magnetic correlations in Sr3Ru2O7 at ambient pressure undergo a qualitative change as the temperature is lowered. Above T*, they are dominated by ferromagnetic instability. However, below T*, the system crosses over to a different behavior, controlled possibly by a canted antiferromagnetic instability.