Sieu D. Ha, R. Jaramillo, D. M. Silevitch, Frank Schoofs, Kian Kerman, John D. Baniecki, Shriram Ramanathan
The rare-earth nickelates (RNiO3) exhibit interesting phenomena such as unusual up-up-down-down antiferromagnetic order and a tunable insulator-metal transition that are subjects of active research. Here we present temperature-dependent transport measurements of the resistivity, magnetoresistance, Seebeck coefficient, and Hall coefficient (RH) of epitaxial SmNiO3 thin films with varying oxygen stoichiometry. We find that from room temperature through the high tem-perature insulator-metal transition, the Hall coefficient is hole-like and the Seebeck coefficient is electron-like. At low temperature the N\'eel transition induces a crossover in the sign of RH to electron-like, similar to the effects of spin density wave formation in metallic systems but here arising in an insulating phase ~200 K below the insulator-metal transition. We propose that anti-ferromagnetism can be stabilized by bandstructure even in insulating phases of correlated oxides, such as RNiO3, that fall between the limits of strong and weak electron correlation.
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http://arxiv.org/abs/1301.1968
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