Quantitative Imaging of Exotic Antiferromagnetic Spin Cycloids in BiFeO3 Thin Films

Understanding how antiferromagnetic spin textures evolve with epitaxial strain and ferroelectric domains in multiferroic BiFeO${}_{3}$ thin films is key for their efficient use as reconfigurable antiferromagnetic spintronic devices. This study combines local-probe techniques to reveal exotic antiferromagnetic cycloids with diverging periods in films under large tensile strain. Coupling quantitative measurements and analytical calculations of the expected stray magnetic field, the authors estimate the spin-density-wave amplitude locked to the cycloid for different strains, and find unexpected deviations of the exotic cycloid direction with respect to the crystallographic axes.