Artificial Superlattices

Artificial superlattices composed of perovskite oxides are attractive model systems for studying low dimensional magnetism via structural periodicity control. Novel magnetic behaviors such as suppression of magnetism at the 2D limit, control of magnetic anisotropy, and modified hysteresis have been observed in oxide superlattices. Consideration on the periodic lattice, epitaxial strain, electronic structure, orbital arrangements, and their couplings is required for the fundamental understanding of such novel magnetic behaviors in the superlattices. In this presentation, we introduce a close relationship between the crystal structure and magnetic orderings in SrRuO₃/SrTiO₃ superlattices fabricated by pulsed laser epitaxy. In particular, the thickness of the SrTiO₃ (STO, a paramagnetic insulator) layers could be controlled to induce an orthorhombic-to-tetragonal structural phase transition in the thin SrRuO₃ (SRO, ferromagnetic metal) layers. The structural phase transition influences the magnetic properties of the SRO layer significantly. Furthermore, the long-range coupling of ferromagnetic SRO layers across the nonmagnetic STO layers will be discussed in the course of understanding the magnetic ground state of the oxide superlattices.