Coupling of magnetic phases at nickelate interfaces

In this paper we present a model system built out of artificially layered materials, allowing us to understand the interrelation of magnetic phases with the metallic-insulating phase at long length scales, and enabling new strategies for the design and control of materials in devices. The artificial model system consists of superlattices made of SmNiO₃ and NdNiO₃ layers, – two members of the fascinating rare earth nickelate family, having different metal-to-insulator and magnetic transition temperatures. By combining two complementary techniques—resonant elastic x-ray scattering and muon spin relaxation—we show how the magnetic order evolves, in this complex multicomponent system, as a function of temperature and superlattice periodicity.

We demonstrate that the length scale of the coupling between the antiferromagnetic and paramagnetic phases is longer than that of the electronic metal-insulator phase transition—despite being subsidiary to it. This can be explained via a Landau theory—where the bulk magnetic energy plus a gradient cost between magnetic and nonmagnetic phases is considered. These results provide a clear understanding of the coupling of magnetic transitions in systems sharing identical order parameters.