Imaging and tailoring electric and antiferromagnetic textures in multiferroic thin films of BiFeO

Antiferromagnetic materials are generating a growing interest for spintronics due to important assets such as their insensitivity to spurious magnetic fields and fast magnetization dynamics. A major bottleneck for functional devices is the readout and electric control of the antiferromagnetic order. In multiferroics, the magnetoelectric coupling between ferroelectric and antiferromagnetic orders may represent an efficient way to control antiferromagnetism with an electric field. In this thesis, we observe a wide variety of antiferromagnetic textures that we control by strain engineering and electric field in the archetypical multiferroic, BiFeO₃. We elaborate epitaxial BiFeO₃ thin films, harbouring various ferroelectric domain landscapes, as imaged by piezoresponse force microscopy. Furthermore, we resort on an inverse phase transition to improve the global electrical order from maze to perfect array of striped ferroelectric domains. Using scanning NV magnetometry, we correlate the antiferromagnetic landscapes to the ferroelectric ones. We demonstrate that strain stabilizes bulk or exotic spin cycloids, as well as collinear antiferromagnetic order. With resonant X-ray elastic scattering, we macroscopically confirm the existence of two types of cycloid. Furthermore, we electrically design antiferromagnetic landscapes on demand, changing one type of cycloid to another or turning collinear states into non-collinear ones. Finally, resorting on anisotropic strain, we stabilize a single domain ferroelectric state, in which a single spin cycloid propagates. This opens a fantastic avenue to investigate the coupling between non-collinear antiferromagnetism and spin transport.