3 <i>d</i> cation substitution for tuning the magnetic properties of ultrathin La-based high-entropy perovskite oxides

A single-crystal high-entropy oxide provides an ideal structure to explore how multication substitution affects magnetic properties. In this study, several ultrathin La-based low-, medium-, and high-entropy perovskite oxides (ABO3) are synthesized through entropy engineering. The B-site cations in the single-crystal ABO3 structure are occupied by transition metals (Mn, Cr, Cu, Co, Ni, and Fe). The effects of multiple B-site substituents on the magnetic properties of the ultrathin nanosheets are extensively characterized via x-ray diffraction, x-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, and magnetic measurements. Some samples of La(MnFeCoNi)O3, La(CuMnFeCoNi)O3, and La(CrMnFeCoNi)O3 exhibit a notable magnetic phase transition from ferromagnetic to paramagnetic states, along with a remarkable enhancement in coercivity. Moreover, these ultrathin samples display low magnetic ordering temperatures due to the structure–magnetic property correlations rather than epitaxial strain, demonstrating flexible and maneuverable magnetic responses.