Thermodynamics of strain engineering in𝑅⁢NiO3(𝑅=Sm,Nd)

Perovskite rare-earth nickelates are a prototypical class of quantum materials that exhibit rich phase-transition physics with promising applications in neuromorphic computing. Although there is existing experimental evidence demonstrating that strain may strongly influence the phase transitions of nickelate thin films, it would be extremely challenging to experimentally construct temperature-strain phase diagrams for different film orientations to guide applications. Here, we use the Ginzburg-Landau theory to formulate the thermodynamics of strained nickelates and calculate temperature-strain phase diagrams of epitaxial SmNiO3 and NdNiO3 thin films with various orientations, which are consistent with the limited existing experimental measurements. We predict that a shear strain can effectively tune the relative magnitude of the magnetic moments on the two nonequivalent Ni sublattices. Our theory provides an efficient theoretical framework for predicting the thermodynamics of strained nickelates, which will provide guidance for engineering their properties through strains.