Variance induced decoupling of spin, lattice, and charge ordering in perovskite nickelates
Alessandro R. Mazza, Shree Ram Acharya, Patryk Wąsik, Jason Lapano, Jiemin Li, Brianna L. Musicó, Veerle Keppens, Christopher T. Nelson, Andrew F. May, Matthew Brahlek, C. Mazzoli, Jonathan Pelliciari, Valentina Bisogni, Valentino R. Cooper, Thomas Z. Ward
Abstract
Perovskite nickelates possess an intimate connection among the structural, electronic, and magnetic orders. We investigate how crystal-field disorder induced by cation size variance impacts the emergence of macroscopic magnetic, structural, and electronic behaviors in single crystal high-entropy oxide nickelate films. The degree of variation in cation sizes hosted on the lattice is found to strongly influence critical ordering temperatures. Resonant x-ray scattering and density functional theory describe how high-variance systems produce local lattice distortions that can be used to manipulate charge disproportionation. The disorder induced shifts to local structure are shown to function as a critical order parameter capable of decoupling the nickelates' distinctive magnetic ground state and metal-insulator transition from its charge ordered state, making it possible to stabilize room-temperature ordered phases not observed in low-variance ternary compounds.