Symmetry Control of Emergent Magnetism in 2D Oxide Monolayer and Heterostructures

We study the magnetism and magnetic anisotropy of the few layer oxides kept in heterostrucutres or superlattices. Despite the challenge of probing the magnetism in monolayer and few layer thicknesses, we performed comprehensive experiments to reveal the nature of the emergent magnetism. Taking the monolayer and bilayer SrRuO3 as examples, we studied one or two layers of SrRuO3 kept in superlattices of (SrRuO₃)_M/(SrTiO₃)_N . We found a number of evidences that indicate the magnetism in such 2D SrRuO3 layers is ferromagnetic. Moreover, we found that the magnetic easy axis of Ru spins in monolayer SrRuO3 is transformed from uniaxial 〈001〉 direction (N < 3) to eightfold 〈111〉 directions (N ≥ 3). This eightfold anisotropy enables 71° and 109° spin switching in SrRuO₃ monolayers, analogous to 71° and 109° polarization switching in ferroelectric BiFeO₃.