Engineering a Spin-Orbital Magnetic Insulator by Tailoring Superlattices

In 5d Ir oxides with an interplay of spin-orbit coupling and electron correlations, we have tailored a spin-orbital magnetic insulator out of a semimetal SrIrO3 by tuning the structure through superlattices [(SrIrO3)(m), SrTiO3] (m = 1, 2, 3, 4, and infinity). We observed the systematic decrease of the magnetic ordering temperature and the resistivity as a function of m. The transition from the semimetal to the insulator is found to be closely linked to the appearance of magnetism at m similar or equal to 3. Long range magnetic ordering was realized even in the m = 1 single layer superlattice, implying that the design and realization of novel electronic phases is feasible at the level of a single atomic layer in complex Ir oxides.