Tunable Magnetism and Morphology of Ferromagnetic Nanocups in Perovskite Ferroelectric Films via Co Exsolution of Transition Metals

Abstract

In complex oxides, delicate tuning of the dimension, scale, shape, and stability of nanostructures is essential to obtain the emergent properties, which are not commonly attained when using the typical thin film growth process. Herein, we demonstrate that the exsolution process, which is modulated by simple doping control, is an efficient method to achieve tunable magnetism and the morphology of nanocups in perovskite ferroelectric Bi3.25La0.75Ti3O12 (BLT) thin films. The multimodal structural and magnetic analyses verify that the codoping of Co and Fe reinforces the phase-separated unique nanocup formation, which is revealed to be a CoFe2O4 spinel ferrimagnet. By employing density functional theory calculations, we show that different doping combinations change the relative exsolution energies of Co and Fe, which may result in the selective formation of nanocup structures. Our study presents a simple and effective methodology for the engineering of nanostructure and multifunctionality in nanocomposite films.