Ferromagnetism in ultrathin surface-free La_0.7Sr_0.3MnO₃ layers in electrostatically defined heterostructures

Electrostatically defined perovskite oxide heterostructures, in which carriers are confined by the modulation of the A-site ion charge, offer new possibilities of tuning the magnetic properties of manganite oxides. We investigate the preferential orientation of ferromagnetic and antiferromagnetic moments in ultrathin La0.7Sr0.3MnO3 layers embedded in antiferromagnetic SrMnO3 as they undergo a metal-to-insulator transition with decreasing thickness. Our results evince the role of orbital occupation, metallicity, and competition of different magnetic phases, in absence of spurious effects occurring in thin films as a result of symmetry breaking at La0.7Sr0.3MnO3 interfaces and of incorporation of oxygen vacancies.