We discussed a particularly interesting interfacial effect-a coupling due to a phase boundary cost-that can be used to achieve fine control over the electronic properties of artificially-layered materials. The artificial model system, presented in this thesis, uses SmNiO3 and NdNiO3-two compounds belonging to the fascinating rare earth nickelate family RNiO3, well known for their sharp metal-to-insulator transition (MIT) observed as a function of temperature. The insulating ground state is also antiferromagnetic. When these two compounds are brought together at an interface the stability of a metal-insulator and magnetic phase separation can be controlled by the thickness of the individual layers. Such behaviors can be explained in terms of a phase boundary cost between metallic and insulating regions, and magnetic and non-magnetic regions, respectively. These results provide a better understanding of the coupling of the MIT and magnetic transitions in systems sharing identical order parameters.