Strong spin-lattice entanglement in cobaltites

Strongly correlated electronic system contains strong coupling among multi-order parameters and is easy to efficiently tune by external field. Cobaltite (LaCoO<sub>3</sub>) a typical multiferroic (ferroelastic ferromagnetic) material, which has been extensively investigated over decades. Conventional research on cobaltites focused the ferroelastic phase transition structure modulation under stress. Recently, researchers have discovered that cobaltite thin films undergo paramagnetic-to-ferromagnetic tensile strain, however, its origin controversial Some experimental evidence shows stress leads valence state of cobalt ions decrease, thus producing spin transition. Other believe stress-induced nano-domain will present long-range ordered arrangement high states, main reason for ferromagnetism oxide films. In this paper, we review series recent researches correlation between lattice degrees freedom in heterojunctions. The reversible film induced structural factors such as thin-film thickness, mismatch stress, crystal symmetry, surface morphology, interfacial oxygen ion coordination, octahedral tilting while kept unchanged, forming highly adjustable macroscopic magnetism. Furthermore, atomic-level precision controllable growth technology utilized construct single cell layer superlattices, thereby achieving ultra-thin two-dimensional magnetic materials through efficient regulation. These advances not only clarified order strongly system, but also provided excellent candidate realization room temperature ferromagnets are required spintronic devices.