  Magnetic anisotropy in atomically thin correlated heterostructures is
essential for exploring quantum magnetic phases for next-generation
spintronics. Whereas previous studies have mostly focused on van der Waals
systems, here, we investigate the impact of dimensionality of epitaxially-grown
correlated oxides down to the monolayer limit on structural, magnetic, and
orbital anisotropies. By designing oxide superlattices with a correlated
ferromagnetic SrRuO3 and nonmagnetic SrTiO3 layers, we observed modulated
ferromagnetic behavior with the change of the SrRuO3 thickness. Especially, for
three-unit-cell-thick layers, we observe a significant 1,500% improvement of
coercive field in the anomalous Hall effect, which cannot be solely attributed
to the dimensional crossover in ferromagnetism. The atomic-scale
heterostructures further reveal the systematic modulation of anisotropy for the
lattice structure and orbital hybridization, explaining the enhanced magnetic
anisotropy. Our findings provide valuable insights into engineering the
anisotropic hybridization of synthetic magnetic crystals, offering a tunable
spin order for various applications.
