Hall effect measurements on epitaxial SmNiO3 thin films and implications for antiferromagnetism

TL;DR

This study investigates the transport properties of epitaxial SmNiO3 thin films, revealing how antiferromagnetic order influences Hall and Seebeck coefficients, and suggesting bandstructure stabilization of antiferromagnetism in insulating phases.

Contribution

It provides new insights into the role of bandstructure in stabilizing antiferromagnetism in insulating RNiO3 films, expanding understanding of magnetic order in correlated oxides.

Findings

Hall coefficient is hole-like above the Nél temperature

Sign crossover in Hall coefficient occurs at the Nél transition

Antiferromagnetism may be stabilized by bandstructure in insulating phases

Abstract

The rare-earth nickelates (RNiO3) exhibit interesting phenomena such as unusual antiferromagnetic order at wavevector q = (1/2, 0, 1/2) 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 temperature 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 antiferromagnetism 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.